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GrainMill Reference

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Glossary Items

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What is GrainMill?

NB – GrainMill also uses conventional integrated Help documentation, on which this HTML documentation is based. Microsoft intends all help to be HTML-based, eventually, but we are retaining the old Winhelp format for the moment (built-in HTML Help requires Internet Explorer v 4, which not everybody is using yet!).

GrainMill transforms a sound by cutting it into small pieces, called grains, then reassembling the grains to reconstruct a new sound. If we simply cut a sound into chunks, then rejoin them end-to-end in the same order, we will end up with the sound we started with! To transform the sound, we need to reassemble the grains in a new way. The simplest grain waveform is a sine wave of arbitrary pitch. However, any input sound can be used, including Frequency Modulated (FM) waves, and sounds such as chirp waves (a sine wave of rapidly increasing pitch), as well as acoustically sampled waveforms.

GrainMill provides us with several 'new ways' to explore: we can stretch out the original sound in time (TIMESTRETCH), we can alter the density of the grains (DENSITY), we can define a 'searchfield' area in the infile from which to select each grain (WANDER), we can change the size (duration) of the grains (GRAINSIZE), we can change the pitch or loudness of each grain (PITCH and LOUDNESS), and we can move them about in space (SPACE). We can also vary the regularity of their spacing in the outfile (SCATTER). Each of these ways to change the sound can be used separately or in combination.

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Getting a basic understanding of GrainMill

For example one can use GrainMill to perform a simple transposition without changing the duration or other sonic characteristics of the outfile. To do this, DENSITY is set to at least 2, TIMESTRETCH is set to 1, a fixed PITCH Pitch change is selected and no random factors are invoked (e.g., by using RANGE(S)). The original sound will be smoothly reconstructed at a different pitch. A somewhat more sophisticated and effective result would be produced if DENSITY were set to about 8 (or preferably a Range between 4 and 12), and a Range of GRAINSIZES was also used.

You can create a simple granulation effect by setting DENSITY to 1. Now the grains are end-to-end and one can hear the way the SHAPING of the grains causes fluctuations in the loudness of each grain.

True granular effects begin to occur when DENSITY is much higher (e.g., 50 to 200), whereby there will be many grains in the outfile where there was just one in the infile. However, to achieve an audible granulation effect, the timing (WANDER and/or SCATTER) and/or pitch level (PITCH) and/or stereo spread (SPACE) needs to be varied randomly, in the case of the latter two by using them with the RANGE option. Without these random changes, grains are simply copied onto themselves and, however high the DENSITY, the outfile will still sound identical to the infile. When each of these many grains is different in e.g. pitch or loudness or source location (WANDER), and the sound is also being stretched out considerably, a complex sonic stream is produced.

GrainMill provides a vast scope of possibilities to explore between smooth reconstruction and massively dense, complex textures in which the granulation effects are dramatically audible.

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How to RUN GrainMill

Explore with an adventurous spirit

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Startup

(You may need to change directories to get to the directory and sound with which you want to work. Click on the  'Working directory' button on the Toolbar.)

You may  want to load settings saved during a previous working session, or one of the examples supplied with GrainMill. Use Open grnfile on the Toolbar (or Load Settings in the File drop-down menu) to load the binary data file for the project. Select the .grn file you want to use – later on, it will also be on the 'most recently used files' portion of the File menu.

You can also launch GrainMill by double-clicking on an existing .grn file, or by dragging a .grn file or soundfile to the GrainMill icon.. With a .grn file, GrainMill will look for an associated soundfile, if given, and attempt to load it. If no soundfile is specified in the .grn file, GrainMill will still start, but will not be able to load the settings.

Finally, it is possible to launch GrainMill from a command line (DOS Console), with a .grn file or soundfile as an optional argument. This method requires GrainMill either to be in your current directory, or in a folder specified in your PATH as given in AUTOEXEC.BAT (recommended).

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Toolbar 

• Open grnfile   –   The 'grnfile' contains all the parameter settings from the main dialog, and some other information such as your 'Working Directory'. You  (or someone else) will have made this file with 'Save Settings' ( See Startup). This is the same as Load Settings in the File drop-down menu.
• Save Settings – You can save all the dialog settings used to create a particular sound, including the names of any breakpoint files used, as well as (optionally) the name of the source soundfile. This saves in a binary file format, and this file can only be opened within GrainMill. To save your settings as a text file which you can view (and perhaps copy into some other document), use Save As Text in the File drop-down menu.
• Open sfile  – You select your infile - the dialog is displayed, with default settings.
• Save Sfile  – This save option is only active if you have selected the Save As option in SETTINGS (box unticked). You are prompted to provide a filename for your sound.
• Stop processing – You can stop the production of your sound if, for example, it's going to take a long time and you can already tell that it is not yet what you want.
• Play outfile – listen to the newly made soundfile. You can also use the Spacebar.
• Stop Playback – can also be done with the Spacebar. The sound is 'rewound' so that the next play starts at the beginning.
• Show Dialog – Restores the parameter dialog box to the screen.
• Settings – Define the main options of your overall working environment. See System Settings.
• Working directory – Select the directory where you will be storing your .grn and .brk files. This can be different from the directory from which you loaded your soundfile. NB: GrainMill only shows .brk files which are in the Working Directory in the Time Contour list boxes. We recommend that you use separate directories for different projects (.grn files and .brk files), to avoid confusion.

Processing a sound with fixed values

Parameters  are named on the left of the dialog, starting with TIMESTRETCH at the top of the screen and ending with SPACE at the bottom of the screen. To the right of these  names are two or three 'radio' buttons, marked L M H for Low, Medium, and High value spans:

You can click on these buttons to select one of three default spans between the lowest and highest values which can be used for that processing option.
The High span will display the highest possible value that can be given. The Medium span enables you to use the slider bar to select among a span of midrange values. And the Low span enables you to move the slider bar through a span of small values.

The value selected in this way is a FIXED value which stays the same as the sound is created.

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Activating RANGE to use a range of values

When you click on the box to the right of the word RANGE,  a second set of controls appears above the original one. Now the lower (original) slider bar is used to set the lower of the two values in this range, and the upper (new) slider bar is used to set the upper of the two values in this range.

You will notice that the program will not let you set a High value (upper slider) which is lower than the Low value (lower slider), nor a Low value (lower slider) higher than the High value (upper slider). The slider just clicks back to the value in the other slider when you try to move it to these illogical positions.

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System Settings

The first of the main options concerns how you save the soundfiles you make. This can be done:

•  TICKED = 'write directly to named outfile' – When you click on MAKE IT, GrainMill writes the new data directly to a new named outfile - you never have to select File->Save As. You can accept the default name written in the output filename box ('OUT' is added to the name of your infile). Or, you can edit this name to alter it in some way. This approach is a little unorthodox for graphic programs (but not unique; and it is also how all command line programs work), and we have found that many users prefer GrainMill to work this way, as you never overwrite a sound without being asked first.
• NOT TICKED = 'use the conventional SAVE AS command' (in the File drop-down menu) - the conventional way of doing things in most graphic programs of this kind. A temporary soundfile is made in the directory allocated for this (the default is the 'system temporary directory', such as C:\WINDOWS\TEMP, but you can choose a different one using the box provided). The outfile name box is removed from the main dialog. This temporary file gets reused over and over each time you MAKE a new sound. The advantage of this second option is that you can make and remake sounds over and over until you're happy with the result and then use SAVE AS. You are not warned that your existing sound will be lost. The temporary file(s) are automatically deleted when you exit.

• NOT TICKED = 'do NOT keep the dialog open when writing and playing sounds' – When you finish adjusting the parameter settings and click on the 'MAKE IT' button, by default the parameter dialog box disappears, as if it were a 'modal' dialog, so that you can see all the grains being drawn in the main window. To resume working, click on the dialog toolbar button (or select the menu option). Your dialog box will reappear unchanged. Of course, the dialog will always be displayed when you open a new soundfile.
• TICKED = 'keep the dialog open when writing and playing sounds' – Now when you finish adjusting the parameter settings and click on the 'MAKE IT' button, the parameter dialog box does not disappear. You will probably want to resize the main window so that you can see both on the screen together. You can play back the sound using the 'Play Outfile' button on the Toolbar and immediately start to make new changes to the parameter settings while you're still listening to the playback (be careful about using the Spacebar in this situation - the dialog may respond to it instead!). In this way you can very quickly fine-tune your sound, moving easily between playback and parameter adjustments. Note however that this option is only likely to be practical  at the higher screen resolutions. The minimum resolution for GrainMill is 800 by 600.

Time-varying values & BrkEdit

This is an example of the simplest possible Time Contour:
0.0 0.0
2.0 2.5

Here, the value rises steadily ('linearly') from zero at the start to 0.5 over 2 seconds. The interpolated value at  time = 1.0 is 1.25.

The time-varying section of the GrainMill dialog box is on the right hand side of the page:

You can enter or browse for the name of an existing .brk file, or you can click on the 'E' (Editor) button to invoke BrkEdit to create or edit a  file graphically. For each parameter, GrainMill sends BrkEdit a default contour, fitting the duration of the infile, which BrkEdit will use if a named file does not exist, or if you select New from the BrkEdit File menu.

Time Contour files can also be written by hand, using a text editor, as in the example above. The one rule about a Time Contour file is that in the first column, giving times, the values must be increasing, and start at zero (GrainMill cannot do time travel!). It is also a good idea (though not, strictly speaking, illegal) to avoid having two successive lines with the same time. This implies an instantaneous change, which usually results in a nasty click or 'glitch' in the sound.

GrainMill and BrkEdit also support  a  new 'extended format' with additional textual information regarding the type of line span (logarithmic or exponential). These tell programs to interpolate using a special curve, rather than a straight line. See the BrkEdit documentation for more information.

If in doubt, use BrkEdit to create a .grn file, and look at that with a text editor (such as Windows 'Notepad') to see what it has done.

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Make ­ Play ­ Continue ­ Restart

PLAY
You can now PLAY the sound you've made. Select Play Outfile from the Options menu, from the toolbar button, or (most conveniently) from the Spacebar. If you see that it's going to be very long and you've heard enough, you can Stop Playback in the same way.

CONTINUE
If you click on the dialog toolbar button, or select View->Show Dialog from the main menu,  GrainMill will restore the dialog box with all your settings and you can carry on making alterations. Alternatively, you can ask GrainMill to keep the dialog box visible all the time by selecting that option via the Options->Settings menu. The dialog will also be redisplayed if you select your current infile from the ‘Most recently used’ list of files under the File menu. If you use the ‘Keep Dialog Visible' option, you can move both the dialog and the main window independently so that the latter is not obscured. The main window can also be resized.

Note that because ‘try and retry’ is likely to be the most common way of using GrainMill, we have tried to minimize the degree of interruption from warning messages. Thus, when you redo a sound, you will not be warned that your current soundfile is not saved.  However, if you are using the ‘Write Directly to Disk’ option, and set the name of an existing file, you will asked be whether you want to overwrite it.

You can change parameters (assuming you are keeping the dialog visible) and click MAKE IT even while a sound is still being played back (this is fastest when using the default temporary-file system) - a series of small changes can be explored very quickly this way.

RESTART
You can select a new infile from the menu so long as no processing is going on; this will reset the dialog box parameters to their default settings. To keep your settings when loading a new soundfile, they will need to be saved to a .grn file. As noted above, GrainMill will not warn you that settings need to be saved!

SAVE SETTINGS
This will create a binary file with the extension .grn which contains the fixed parameter settings and the names of any breakpoint files used to create your sound. Optionally, it can 'associate' your infile name with the settings. A .grn file including an infile association can be used to launch GrainMill - so long as the infile is where it is claimed to be! You might like to think of a generic .grn file without an infile association as  a 'preset', and  a .grn file with an association as a 'project'.

LOAD SETTINGS
Load a .grn file, as created above.

SAVE AS TEXT
This saves the settings in the dialogue box as a text file as a way of documenting your work. It cannot be re-loaded. The binary .grn file is intended for re-loading.

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Using Range to set a a group of changing values

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Shaping grains to avoid clicks

It is not possible simply to chop up sound as if with a knife. If you do this, you will produce a click where the cut sound ends, because the volume is likely to fall off a cliff, as it were: from high to nothing within an instant. Among other things, the physical mechanism reproducing the sound for our ears cannot cope with such an abrupt change. To avoid this, we use a tapered cut, called a 'splice slope':

A splice crescendos from silence at the start of the sound (its 'attack'), or decrescendos into silence at the end of the sound (it's 'decay') ­ though butt joins are also possible (no sloping envelope at all). In this case, the 'sound' is a single grain. However, we usually don't want to hear these little crescendos and decrescendos in our new sound because of the tremolo effect produced by the (very) rapid fall-rise-fall-rise etc. in volume. It is for this reason that the program overlaps the grains a little, so that the crescendo on the following grain comes in as the previous grain decrescendos, thus maintaining a certain consistency of volume.

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Stretching time with GrainMill

When the TIMESTRETCH slider bar is set to a value greater than 1, grains which overlap are cut from the infile and then reassembled in the outfile in such a way that they do not overlap as much, thus stretching out the sound.

When the TIMESTRETCH value is 1, there is no change.

When the TIMESTRETCH value is less than 1, grains which do not overlap are cut from infile (there may even be gaps between these grains: bits of soundfile missed out) and then reassembled in such a way that they do overlap, thus shrinking the sound.

The upper limit of TIMESTRETCH can be very high and should be used with caution (i.e. not with a long infile!). If you find you have done this by accident, it is always possible to stop processing - you are not required to wait for it to complete!

The 'Length' box at the bottom of the dialog box shows the effect of changing both TIMESTRETCH and GRAINSIZE. The duration is a maximum estimate, and can be edited if necessary.

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Altering the density of the sound texture

As DENSITY becomes increasingly greater than 1 (more dense), the grains overlap more and more, producing a continuous to smooth/dense sound. For example, when DENSITY is set to 5, there will be 5 grains in the outfile where there was 1 grain in the infile, i.e., 5 grains overlapped where previously there was only 1 grain. When one or more of the RANGE options are activated, each of these 5 grains will be separately processed. This is how the outfile becomes more and more complex. Densities of 50, 100, or even 200 simply make the outfile texture more and more complex ­ depending on the other settings. The upper limit in this program is 256. High densities are most likely to be needed when creating stereo sounds, or when spreading over a very wide pitch range.

As DENSITY becomes progressively less than 1, we begin to hear silences between the grains. If the grains are very short, and the density is only just below 1, this will appear as a kind of grittiness in the new sound. But if the density is nearer to 0, the new sound will contain a sparse texture of isolated grains or droplets.

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Adjusting the size of the grains

Furthermore, if the grains are very, very, very short, they will contain so little information from the original sound that its qualities will be destroyed. So there is a lower limit on the size of the grains. If your grains are about 50 milliseconds in length (0.05 of a second), they will happily capture the qualities of your sound.

Once the grains become much longer than this, we create a different effect. Almost every natural sound changes through time: it changes pitch, loudness, and its timbre. If you are using grains to timestretch a sound to double its length, the grains you cut from the original sound will use overlapped portions of the original sound. In fact, each grain will contain a copy of half the previous grain.

If the original sound is itself changing, and your grain is sufficiently long, the sound inside the grain will itself be changing. When you now place the next grain after the first, you will hear that change in the sound being repeated ... the output sound will seem to backtrack to a place earlier in the change-process. There will be a kind of very fast echo inside the sound.

These 'internal echoes' may be a very interesting effect if this is what you want to hear. However, if you just want to make your original sound longer, you need to minimize this echoing. It turns out that a grainsize of around 50 milliseconds (0.05 sec) captures enough of your sound to retain its special sound quality, but not so much of it that you are able to hear any change in the sound within the grain. Using grains of about 50 to 60 ms allows the sound to be stretched without any sense of internal echoes. As complete regularity in grains can sometimes lead to undesirable phasing effects, a good idea is to use a RANGE to select grainsizes between, say, 40 and 90 milliseconds.

Grainsizes longer than 50 ms allow more of the original sound to come through. A sandy beach reveals very little of the shape and quality of the original stones from which the sand was ground, but shingle is much closer to the original shape and texture of the rock from which it was formed. Note that there is a relationship between the type of input sound and the effect a given grainsize will have. The sharper (faster) the attack transient in the infile, the more it will be present in the grain, even with a fairly short grainsize, and certainly with a grainsize as long as or longer than this attack transient.

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Using a range of grainsizes

A very good range to choose is between 50 ms and 80 ms. Ranges greater than 100 ms (0.01 sec) will begin to produce collage-type textures, i.e., sounds in which portions of the infile are distinctly recognizable.

On internal echoes

If you:

• choose grains not quite in exact sequence (by using WANDER), and
• place them in slightly randomized positions in the output sound (by using SPACE), and even
• use a slight microtonal variation of pitch (by using PITCH), and
• make small variations in loudness (by using LOUDNESS), and then
• create a higher density (by using DENSITY)

Once your grains start to become any larger than 50 ms (0.05 sec), you will generate obvious echoes inside your reconstructed sound. If your grains are 'very' long (e.g., 1 second) and if you use the WANDER process over a very large span, you will produce a kind of random collage of pieces of your original sound.

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Wandering grain locations

With WANDER set to 0, grains are selected from the  infile in the strict order in which they were cut in the first place With WANDER set to (say) 0.1 sec (100 ms), a grain is chosen from the infile within a range of 0.1 seconds before the 'true' position. In other words, there is a certain vagueness about the order of the grains chosen for use in your new sound. The larger the WANDER, the more vagueness there is!

And if you set WANDER to cover the entire length of the original sound, then the vagueness will be complete: your original sound will become completely scrambled. It is useful to know that the searchfield gradually expands when it is set to the length of the entire soundfile. GrainMill reads through the infile, and as it does so its 'here' position is moving through the file. The searchfield is from the beginning of the file to 'here' and thus gradually gets larger and larger. This means that the scrambling effect will be somewhat minimal at the start and then increase steadily. This transitional process from smooth to chaotic can be useful musically.

In this extreme case, the infile is not so much a single source sound, but a sort of database - any part of it may appear anywhere in the outfile!

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Moving the pitch of grains up or down

The span of pitch change values is roughly based on 12, so that each integer change represents a transposition of more or less 1 semitone.

Values less than zero (i.e., negative values, such as -0.5) transpose the grains downwards in pitch. Remember to precede the number with a minus sign!

Note that altering the pitch also alters the length of the grains (higher pitch shortens grains, lower pitch lengthens grains. However, if you set TIMESTRETCH to 1, the duration of the outfile will remain the same as the infile, because of the way the grains are reassembled.

When you activate the RANGE button, a second slider appears and you can set lower and upper limits to a range of transposition values. The program will then, for each grain, select a transposition value at random from somewhere within this range. The sonic results of these random jumps of pitch can vary remarkably as the size of the range is increased.

GrainMill works hard to ensure that the quality of transposed grains is as high as possible, but with extreme transpositions, some loss of quality (or, at least, some change in character) is likely. Most importantly, GrainMill does not filter each grain (it would add too much time to the processing), so if the infile contains  a lot of high-frequency sound, and you set a high upwards transposition, those high frequencies may end up too high for the sampling rate of the file. This is called 'aliasing', and is heard as unexpected low frequencies appearing in the sound, and sometimes a sort of added buzziness. If this becomes a problem, then you may need to use an external sound editor (or the filtering programs in the CDP system, of course!) to filter out the higher frequencies in your source sound.

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Controlling the loudness of the grains

When you activate the RANGE button,  you can set lower and upper limits to a range of loudness values. The program will then, for each grain, select a  level at random from somewhere within this range. Having a range of random loudness values in the texture adds a great deal to the character of a granular sound. It is especially worth experimenting with GRAINSIZE, to get different effects.

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Timing scatter of output grains

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Spatial location

When RANGE is activated, a second slider bar appears and a specific range can be selected, usually using the lower bar for the Left limit, and the upper bar for the Right limit.

Full Left on the lower slider bar + full Right on the upper slider bar sets the full stereo field as the range within which each grain is randomly positioned. This can be tightened by moving the sliders more to the middle.

If both sliders are set to Centre (the defaults), the program will produce a mono outfile (making it pointless to use the RANGE option). Note that any non-zero SPACE value will cause the program to produce a stereo outfile. However, the sound can be located on only one channel of this stereo soundfile if either:

a single (fixed) value to the Left or Right of Centre is used,
OR
both sliders are close to the Left or Right.

Problems?

• Duration.

 If  GrainMill successfully makes an outfile, but it does not have the time-varying characteristics you expected,  one possible reason is that the Time Contour files do not have the correct duration for your infile. This will happen frequently as files created for one sound are reused for another. If GrainMill reaches the end of a Time Contour file while it still has some processing to do, it  uses the last value from the file, as if there were a constant-level span there.
• Overlaps

Any overlap between Low/High pairs of Time Contours, or between a Time Contour and an active fixed value, will force GrainMill to stop, and display an error message, identifying the parameter which had the problem. Values can be identical, but a Low value cannot be above a High value. The comparison facility of BrkEdit is provided especially to resolve this problem. Start with the file you want to edit, and then load in the other one as a Comparison File. Click 'Align Vertical' to make sure the displays show the true relationship. Any overlaps should now be easy to spot. In those cases where the vertical resolution of the screen is just too coarse to show up very slight overlaps, you will need to use a text editor to tweak the values.  Sometimes, just changing the Slope of a non-linear span can be enough to create an overlap.
• Glitches

if you hear unwanted clicks or thumps in your outfile (not attributable to soundcard or driver problems), it is possible that one or more of the spans in a Time Contour is a little too steep. Before assuming GrainMill has a bug (though we freely acknowledge this is possible), check your Time Contours, and if necessary test them individually.  This problem can also arise indirectly as a result of a duration mismatch.

If you do discover a problem that does appear to be a bug, well, of course, we want to know about it! We will need to have quite a lot of information form you about your system (processor, speed, memory, OS, etc.), and also (depending on the nature of the bug) information about your source sound (such as duration, sample rate, peak amplitude) and parameters. Ideally, we would need your .grn file and any Time Contour files you are using, so that we have the best chance of reproducing the problem.
 
 
 

Introduction

The FILE Menu – Startup, Save & Compare

As shown by the File dropdown menu, you can proceed in three ways:

1. NEW – create a new breakpoint file, or
2. OPEN – open an existing breakpoint (text) file, or
3. EXTRACT FROM SFILE – extract an amplitude envelope from an existing soundfile. Note the Hide Span Handles option above the main display. Ticking this option will remove the black squares ('handles') marking the breakpoints. An extracted soundfile may have 10's or 100's of these all bunched together, so it is sometimes useful to see the breakpoint shape without them. Ticking on 'Hide Span Handles' again will remove the tick and restore the black squares: the button is a toggle.

1. SAVE – saves as a text file of separate lines containing the data pair time value. Any non-linear segments (logarithmic or exponential) will automatically be converted to linear segments which approximate the curve.
2. SAVE EXTENDED – save in extended format, which defines non-linear segments using additional text fields.  For example, you will see a line such as the following:

0.476079 0.411255 exp 5.500000

These show, from left to right: time, value, line type, and line setting. The default linear line type requires just the time and the value.
The extended format is new, and not yet fully supported by other CDP programs, though it is of course recognized by GrainMill.

In both save options, you are prompted to enter a filename. The default extension is '.brk'. This is not mandatory, but has the advantage that all .brk files are automatically displayed when OPEN is selected, and will be found by GrainMill..

You can save to the same name if you wish. You are notified that the file already exists and asked if you wish to overwrite it.
 

3. SAVE AS AUDIO – saves the breakpoint shape as an audio soundfile. This will save in the mode (Amplitude or Frequency) in which you are currently auditioning the shape. You can set the Sample Rate and the Sample Type in the SETTINGS menu under OPTIONS. Sample rates available are 96000, 88200, 48000, 44100, 32000, 22050, 18000 and 11025. Sample type can be 16-bit short or 32-bit float.

1. COMPARE WITH ...
• Click on COMPARE WITH ... in the FILE menu to open a second breakpoint file. It will be shown in red, and cannot be edited.
• Data relating to this second file is now displayed in the 'Compare File' box at the left above the breakpoint display. It is likely to have a duration and range which is different from that of the file you're working on (the range is shown with the 'Data maxval' and 'Data minval' fields), but by default the display shows it as it originally appeared on the screen. 'View maxval' and 'View minval' shows what the view range of the comparison file actually was.
• If you click on the Align Vertical button, the vertical range setting is altered to match that of whichever of the two files has the largest vertical range – you see the 'View maxval' and 'View minval' fields alter accordingly. You can then see the ranges of the two files proportional to one another within the same range. The vertical range can then be adjusted, if you wish, so that you can view the two, now related, ranges within any chosen vertical range.
• If you click on the Align Horizontal button, the display now adjusts the comparison file so as to show its true time location within the duration of the current breakpoint file on which you are working.
• Both of these facilities are especially useful when working with breakpoint files for low and high range limits, because they are not supposed to overlap, though they can touch (have identical values).
• You can also EXTRACT the envelope of a soundfile as a breakpoint file and in this way see your breakpoint file laid out against the shape of the sound itself. (The extracted envelope will be much easier to see if you tick 'Hide Span Handles'). The resolution of the extraction process is very fine, and you will find that in most cases you can REDUCE the number of points considerably without losing the essential shape - REDUCE takes special care with amplitude data to preserve low-level detail.. Thanks to the UNDO facility you can compare the effects of REDUCE  against the original data, both visually (if you load the original data as a Comparison file) and sonically, using PLAY.
2. CLOSE COMPARE – enables you to remove the (red) comparison file from the display.

Using the Breakpoint Editor

1. Select and move a point – place the tip of the cursor arrow on a point 'handle' (the small black square), click and hold down the left button. You can now drag that point left or right, up or down. As you do so you will see the displayed time and value of this point change.
2. Insert a new point – double-click on a line at about the right time location along the line. This will insert a point at that location. You can now move it as in Action 1.
3. Delete a point – a single click will select a point for deletion. It will turn red in colour. To delete it, then click on the Delete Point button. If you change you mind while the point is red (selected for deletion), but before you actually delete it, just click somewhere else within the breakpoint file display screen and the point will turn black again, thus cancelling the Delete Point action.
4. Select a line span – a single click on or close to a line with the left button will select it. A selected span will turn green, and will be drawn as a dotted line. You can cancel this action by clicking somewhere else within the breakpoint file display.
5. Alter the type of line span – first select a line span as in Action 4. Now go to span settings and click on the radio button for the type of line you want. You will see the line change shape when you select a different type. The slider to the right of the line types can be used to increase the intensity of the shape: you will see the shape change as you move it. Note that the curve of the logarithmic line starts with a fast rate of change and then slows down, while the exponential line starts with a slow rate of change and then speeds up. You can also move the end points of the line while it is still green and see how this affects its shape. These curves enable you to make your breakpoint shapes more fluid, and musically more 'natural' - especially for Amplitude (Loudness) and Pitch Contours.

Zoom/Scroll

• The left trackbar zooms starting at the beginning of the file, stepping in towards the end. You can click along the bar line, or drag the slider. You see the display move further into the file, stretching the displayed distances between points at the same time.
• The right slider zooms starting at the end of the file, stepping in towards the beginning. You therefore see the front part of the file expand as the later sections disappear off the right of the screen.

PLAY/STOP (Audition)

In the Amplitude mode you hear a single pitch, the volume of which changes according to the breakpoint shape on the screen, over the length of time set for the breakpoint file. This is especially useful when, for example, you have extracted the amplitude envelope from a soundfile and want to hear it in the abstract, imagining what it might be like imposed on another soundfile. It is a very clean and simple way to hear what the shape is really like. The vertical range (whatever it may be) of the breakpoint window is converted internally to the range  0 to 1 to control the amplitude of the internal oscillator. The frequency of the single tone can be set from the SETTINGS dialog. You will hear, for example, that logarithmic and exponential spans tend to have a more 'natural' sound than linear ones.

In the Frequency mode you hear a pitch glissando moving through the breakpoint shape on the screen, over the time of the file. In SETTINGS, you can set High and Low limits in Hz for the frequency range to be heard.

• A help to mentally imagining the effect the shape will have. Just as the orchestrator develops the ability to hear the effect of various combinations of instruments will have, so the electro-acoustic composer needs to develop the ability to imagine mentally the effect a breakpoint shape will have on a given parameter and the sound as a whole. It is important to take the time to engage in this mental process. For example, if a time-varying shape is to be applied to grainsize in a granular synthesis process, one should mentally listen to the grains getting larger and/smaller as the sound unfolds. Auditioning the breakpoint file at the same time can help with this mental exercise.
• Auditioning a breakpoint shape in the two different modes, Amplitude and Frequency, has useful educational benefits. For example, it illustrates how much more sensitive the ear is to frequency than to amplitude. Small changes in the shape that are quite clear as pitch changes, may be inaudible or scarcely audible as amplitude changes.
• BrkEdit can be used for synthesizing basic sounds for use with GrainMill (or other programs). For example, try creating a 'chirp' sound by making one or several line segments which increase in value over time. Sounds of this kind are also often used as test signals, e.g. for a filter.

The Edit Menu

1. LENGTH – there are three ways to alter the length of the breakpoint file. For the first two of these, you first enter the length you would like it to be. Then you select either:
1. Truncate/Extend the file ­ if the length you have specified is shorter than the existing breakpoint file, the file will be truncated by removing one or more segments from the end of the file; if the length you have specified is longer than the existing breakpoint file, a new segment will be added to the end of the file to bring it up to the required length. Or,
2. Shrink/Stretch the file ­ in this case, all the segments of the breakpoint file are made proportionately smaller or larger so that the whole file fits – is scaled to – the new length specified.
3. Get length from soundfile ­ alternatively, your existing breakpoint file can be rescaled to match a specific soundfile. In this case you may need to browse your directories for the right soundfile. Click on the 'BR' button to begin browsing. When you have selected the soundfile and have clicked on OK, the breakpoint file will be rescaled to fit the soundfile you've selected.
2. ALL SPANS TO LINES – this function converts the logarithmic or exponential curves into a series of linear segments.
3. VERTICAL RANGE – the default vertical range for the breakpoint file is from 0.0 to 1.0. The Maximum value can be raised, and the Minimum value can be lowered (into the minus range). This is useful to get the values produced by the editor to match the range of values required by a specific parameter. For example, some of these are from the -1.0 to 1.0 range, so you would adjust the vertical range. You will notice that if you do this for an existing breakpoint file made with the vertical range set at 0.0 to 1.0, it will at first only occupy the upper half of the display: because the lowest value so far was 0.0. However, you can now drag points down into the negative part of the range.
4. REDUCE – this reduces the number of points used to express the shape of the breakpoint file. This facility has been provided because sometimes, when the breakpoint file has been extracted from a soundfile (i.e., is the shape of its amplitude envelope), the screen ends up jam-packed with points. Reduce removes points to the degree specified by the threshold, preserving as intelligently as possible the original shape. This makes the file easier to handle and adapt. The value you set for threshold defines the range within which points are reduced. It should normally be a small fraction of the overall vertical range. Anything in the Amplitude range (0 to 1) is treated specially, to preserve low-level detail.
5. TRANSFORM VALUES – calls a dialog box with a list box with four methods:
• SCALE VALUES – this will multiply the values in a breakpoint file by a constant factor. For example, multiplying by ½ will halve all the values. A '-1' will invert the signal.
• OFFSET – this will add a constant to all the values. The constant may be a negative number.
• WARP – this applies squares or square roots to the values in the breakpoint table. Some remarkable shapes can be achieved with this function. The warping process first internally rescales the values of the existing breakpoint table to lie between 0 and 1. For example, 0 2 4 6 becomes 0 .33 .67 1. The mathematical effect of the warp factor is based on the fact that it is operating on values less than 1. This is what happens:

Warp factors > 1 will push values towards the minimum (positive numbers will move downwards towards 0, negative numbers will move upwards towards 0) – a squaring process.
Similarly, warp factors < 1 will push values towards the maximum (i.e., away from zero) – a square root process.

Warp Values & Shapes

original value	warp factor	resulting value
positive & < 1	> 1 (square)	becomes smaller, trace descends towards 0
negative & < 1	> 1 (square)	becomes smaller, trace rises towards 0
positive & < 1	< 1 (square root)	becomes larger, trace rises towards top
negative & < 1	< 1 (square root)	becomes larger, trace descends towards bottom
0 or 1	any	no change

When 'values become smaller', they are drawn towards zero. This means that positive values will descend (and negative values will rise).

When 'values become larger', they move away from zero. This means that positive values will rise (and negative values will descend).

Traces which cover a -1 to +1 range will have a double bend in them.

You can study this function by creating a breakpoint file with a number of points in a rising or falling straight line,  spaced time-wise as you wish. Then apply a warp factor > 1. You will see the line rising slowly at first, and then curving upwards more rapidly. Now apply a warp factor which is < 1. You will see the line rising rapidly at first, and then curve upwards more slowly. Finally, change the scale to lie between -1 and +1. Warp factors < 1 and > 1 will both induce some form of 'S' curve. The Play facility in Frequency mode gives an even better indication of what is happening.

• RECIPROCATE – this is a special, somewhat experimental, facility which has been supplied to help overcome a difference between the previous GRANULA program and the new graphic GrainMill program. In GrainMill the timestretch parameter is set as a multiplier; e.g., a '2' means twice as long. In GRANULA, the reciprocal of this is used in the velocity parameter: e.g., ½ or 0.5. RECIPROCATE can be used to convert breakpoint files created for velocity in GRANULA to the form used by GrainMill. RECIPROCATE can have strange effects on other breakpoint files, so should be used with caution.
6. UNDO – the program records your operations on the file so that it is possible to backtrack through a series of UNDOs. Note that this does not apply to adding and deleting points, which you can easily do on the screen. Rather, it applies to major global changes to the files, such as New and the EDIT menu: Length, Span to lines, Reduce, Reciprocate and Scale – not Vertical scale, which only affects the display.
7. REDO – this steps back through your UNDOs, restoring the previous state of the file.

The Settings Menu

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The Help Menu

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The infile

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The outfile

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What is a 'grain' of sound?

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Decibels: a measure of loudness

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Milliseconds: a measure of time

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Timbre: a description of tone quality

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Splices: Butt and sloping joins

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Panning a sound

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Mono Soundfile

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Defaults

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Attack - Sustain - Decay

Experimenting with BrkEdit is one of the best ways of exploring amplitude envelopes.

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