MUSIC BOX

By David Snow

Released as Freeware June,2000

Algorithmic composition software for the Atari ST (monochrome only)
This is an enhanced version of a do-it-yourself software project that appeared in the March 1989 issue of Electronic Musician magazine. MIDI Music Box is an algorithmic composition program that can be best described as a four-track sequencer that generates its own tracks. In the original bare-bones version, user interaction was minimal: pressing "G" on the computer keyboard would cause the program to generate four monophonic tracks on MIDI channels 1, 2, 3 and 4; pressing the "P" key would play the tracks; and pressing the "T" key would allow you to change the playback tempo. The tracks were generated from rhythmic source patterns that were strung together in random order; pitches were chosen randomly from a source set. Since the source rhythms and pitches were coded into the program, you had to mess around with the BASIC listing if your wanted to alter them. I wrote this version to allow one to more easily change the rhythms and pitches, and also to add functions to modify the generated tracks. Although it's more user-friendly than the original, it's not exactly "intuitive" to operate, so here are brief instructions:

1. Hook the MIDI output of your ST to a 4-channel multitimbral synth (or four single-channel synths) which is set to receive MIDI data on channels 1, 2, 3 and 4. Hook the MIDI out of the synth (or a keyboard controller) to the ST's MIDI input.
2. Run the program (duh).
3. Before you can make music, you need to program Music Box with rhythms and pitches:
a. Click on the EDIT RHYTHMS button.
b. You'll see a dialog box with 8 four-note rhythm patterns. The default patterns are all quarter notes, which is very, very boring. To change a note value in a rhythm pattern, left-click on the note until you get a value you want; you can also change any note into a rest. If you want to make a rhythm pattern that is shorter than four notes, click on a note until it changes into the "END" icon; the pattern will only play the notes before it. If you want fewer than 8 rhythm patterns, change the first note in any pattern into the "END" icon; it will be skipped when the tracks are generated.
c. You can save the set of rhythms by clicking on the SAVE button, and reload them later by clicking on the LOAD button (double-duh). When you're finished editing rhythms, click on the QUIT button.
d. Click on the ENTER PITCHES button.
e. Enter pitches using your MIDI keyboard or controller. Note-entry will automatically end if you enter 12 notes. If you want to enter fewer than 12 notes in your pitch set, quit by pressing the "Esc" key on the computer. The pitches are displayed on a piano-style grand staff as you enter them.
4. Along the left side of the screen are ten Function Buttons that create or modify the 4 tracks, which are designated A, B, C and D. To make a Function Button affect the desired track, select the A, B, C or D button before clicking the Function Button. To wit:
RHYTHM: Randomly fill the designated track with patterns from the EDIT RHYTHMS dialog.
PITCH: Assign pitches from the ENTER PITCHES dialog to the randomly created rhythm track.
COPY FROM/COPY TO: Clone one track to another.
TRANSPOSE: Raise or lower the pitch of a selected track by the value indicated in the "Transpose value" edit field; a negative number lowers pitch.
COMPRESS: Divide the rhythm/duration values in a selected track by the factor in the "Compress ratio" edit field.
EXPAND: Multiply the rhythm/duration values in a selected track by the factor in the "Expand ratio" edit field.BR> SHIFT: Delay the start of a selected track by the value indicated in the "Shift value" edit field. A value of "24" equals one beat. Do the math.
INVERT: Turn the pitch intervals in a selected track upside down.
REVERSE: Reverse the order notes in a track.
Whenever you click on a Function Button, you change all the notes in the selected track; there is no "Undo" function.
The PLAY button does what it says; select playback tracks using the A, B, C and D buttons.
The AUTO-GENERATE button generates all 4 tracks and starts playback immediately. The MIDI FILE button saves the tracks in SMF format.
Neat trick: Edit rhythms and enter pitches as described above, and generate the "A" track by clicking on the RHYTHM and PITCH Function Buttons. Copy track A to tracks B, C and D with the COPY FROM/COPY TO function. Enter a value of "96" in the "Shift value" edit field. Select the "B" button next to the SHIFT Function Button, then click the SHIFT button. Select the "C" button next to the SHIFT Function Button, then click the SHIFT button TWICE. Select the "D" button next to the SHIFT Function Button, then click the SHIFT button THREE TIMES. Now play the four tracks: instant 4-part canon.

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NEW PROGRAMS AVAILABLE FROM DAVID SNOW: SEPTEMBER 2000

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Phraser, an interactive real-time MIDI file generator for the Atari ST/TT/Falcon family of computers

by David Snow
Released as Freeware SEPTEMBER 2000

Instant psuedo-12-tone composition is here! Hook up a MIDI keyboard to your ST's MIDI output and double-click on PHRASER.PRG. At the first prompt, enter a tempo (beats per minute) value. At the second prompt, enter a beat-subdivision value (2=eighth notes, 3=eighth note triplets, 4=sixteenth notes, etc.). Start playing single notes on the MIDI keyboard. Phraser responds by creating random phrases triggered by the notes you play. Note density is controlled by how loudly you play. To quit, press the Esc key. You can save the performance as a MIDI file, or click on "Cancel" in the file selector to discard it.

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NEW WAVE
A MIDI Sound Design Tool for the Falcon030
by David Snow
Released as Freeware SEPTEMBER 2000

New Wave is a GEM application that allows you to create original 16-bit sound files using a powerful technique called "additive synthesis". New Wave samples can be downloaded to any sampler or sample-player that supports the MIDI Sample Dump standard, and also be saved to disk in Sound Designer format. Even if you don't don't own a sampler, you can still audition the samples you create.
A little theory...
It's beyond the scope of this manual to delve deeply into the science of acoustics, but some background is necessary to understand how New Wave works.
Sound is energy produced by a physical medium vibrating at a rate called its "frequency". The higher the frequency, the higher the pitch of the sound. When a trumpet or a violin plays the note "A" above middle C, the frequency of air vibration is 440 cycles per second (or 440 Hertz).
The tonal quality that distinguishes the sound of a trumpet from a violin (or from a power saw, for that matter) is called its "timbre". Several elements combine to create that psycho-acoustic effect; one of the most important of these is the presence of "partials", which are low-amplitude frequencies superimposed upon the basic or "fundamental" frequency. For pitched instruments like violin and trumpet, the ratios of the frequencies of partials to that of the fundamental is usually an integer: the first partial is twice the frequency of the fundamental (2:1), the next is three times the frequency of the fundamental (3:1), the next four times (4:1), and so on. The amplitude of these paritals is so low that you don't hear them as separate notes; instead, they blend with and color the fundamental so you hear only its pitch. Different instruments accentuate different partials; a clarinet timbre, for example, is composed predominantly of partials with odd-integer ratios: 3:1, 5:1, 7:1, etc. For unpitched instruments like drums and cymbals, there is no fundamental frequency per se, and the partials may all be of nearly equal amplitude in non- integer (fractional) ratios to each other.
Another parameter that gives a sound its character is its "amplitude envelope", or the manner in which it changes in loudness over time. Percussive instruments have a virtually instantaneous "attack", followed by a sloping release into silence. By contrast, brass instruments have slower attack (slower on a scale of milliseconds, that is) which peaks and quickly decays to a steady state ("sustain"), then releases when the player stops blowing. In reality, each partial in a complex acoustic sound has its own amplitude envelope contributing to the overall loudness contour. The frequency of a partial can also change over time (although in acoustic instruments it usually deviates only by a small fraction). This frequency curve is called a "pitch envelope".
The logic of "additive synthesis" is to build sounds from the bottom up by adding partials together. In order to create interesting, dynamic timbres it's necessary to provide a sufficiently large number of partials for tonal variety, and to equip each with its own frequency ratio, and amplitude and pitch envelopes.

Using New Wave

New Wave offers three methods for creating sounds. The first method, "Single partial editing", is available on the Partial Editing Page which is the first screen you see. On the top half of the screen is the Amplitude Envelope window, and on the bottom half, the Pitch Envelope window. To draw an envelope in either window, click and drag the mouse: left-clicking and dragging allows you to free-draw the envelope, while clicking both buttons and dragging lets you stretch a straight line from the starting point.
New Wave permits you create envelopes for a maximum of 24 partials. To select a partial for editing, select "Partial #" under the Edit menu and type in the number of the partial you want. You can also select partials by using the up and down cursor keys on the computer keyboard.
Each partial has a frequency ratio and waveform assigned to it. To change these parameters, select "Waveform" or "Ratio" from the Edit menu. By default, each partial is a sine wave with a frequency ratio equal to its partial number (i.e. the second partial has a ratio of 2:1, the third 3:1, etc.).
Under the Edit menu you'll find options for manipulating amplitude and pitch envelopes. "Copy" lets you copy the envelope of the currently selected partial to other partials. "Swap" exchanges the envelope of the current partial with that of another. "Shift" moves the envelope up or down by a positive or negative offset value; "Scale" modifies the slope of the envelope by multiplying it by a factor of 0% to 200%. "Invert" flips the envelope upside down, while "Reverse" flips it backward. Finally, "Reset" restores the envelope to its zero-state.
You can perform these edit options on either amplitude or pitch envelopes. Make sure the proper window is selected before executing an edit option, or you'll alter the wrong envelopes. To select a window, click on it, or click on "Amplitude" or "Pitch" under the Edit menu. With "Pitch envelope" selected, you can also define the maximum span of pitch deviation by clicking on "Pitch span" under the Edit menu.
You can view all envelopes simultaneously by clicking on "All partials" under the "Display" menu; the currently selected partial will be drawn in a heavy line. You can't manually draw envelopes in this display mode, but all options under the Edit menu are available. "All partials" will display either amplitude or pitch envelopes, depending upon which edit mode you're in. Click on "Amplitude" or "Pitch" under the Edit menu to change edit mode.
Once you have created envelopes, you must define the parameters of the sample that you wish to generate. Click on "Set pitch" under the Sample menu: a 5-octave keyboard will appear. Left-clicking on a key sets the pitch of the sample accordingly and displays the frequency of the note. Right clicking closes the keyboard.
Next, select "Parameters" under the Sample menu. The top edit field displays the frequency of the pitch you just entered (which you can also enter directly). Enter the desired duration of the sample in the middle edit field, and the sampling rate in the bottom field. New Wave samples can be a maximum of 64K 16-bit words long; the maximum duration of a sample therefore equals 65536 divided by the sampling rate.
Once parameters are set, click on "Calculate" under the Sample menu. To view the waveforms of the generated sample, select "Wave display" under the Display menu. You can also view the waves sequentially by selecting "Wave sequence"; pressing the Control key halts the sequence for viewing. To hear the sample, select "Audition" under the Sample menu.
To dump the sample to a synth, make sure MIDI IN and OUT cables are properly connected between computer and sampler. If the sampler is set to receive dumps on a particular MIDI channel, set New Wave accordingly by selecting "Channel" under the MIDI menu. Now click on "Sample dump" dump under the MIDI menu. You can abort a dump at any time by hitting a key on the computer. If your sampler doesn't have a keyboard, you can play it directly from the computer by selecting "Keyboard" under the MIDI menu and clicking on its keys.
To save a sample to disk, select "Save sample" under the File menu. You can also save and load parameter files containing envelope, waveform, ratio, pitch, duration, and sample rate information by selecting "Save parameters" and "Load parameters" under the File menu. (Note: In 1993, I made the unfortunate decision to give New Wave parameter files a ".WAV" extension. Sorry about that. This program was developed before I had heard of Microsoft WAV-format audio files.)
You can selectively re-initialize envelopes, waveforms, and frequency ratios by selecting "Reset all" under the Edit menu. Click on the buttons representing the parameters you wish to reset, then click on "OK".

A Slice of Time

The second method of generating samples is called "Timeslice editing". Instead of editing one partial at a time (with each envelope representing the entire duration of the sample), you can edit all the partials at discrete points in time.
Select "Timeslice" under the Display menu. At the top of the screen is a series of buttons that represent 32 equally-spaced time segments (i.e. for a 1 second sample, each button would represent 1/32 of a second). At the bottom of the screen are 24 "volume control sliders", each representing the amplitude of a partial at the selected point in time; click and drag each slider to the desired amplitude level. After editing the partials in a timeslice, click on the MARK button. To select a new timeslice to edit, click on a button under "AMPLITUDE ENVELOPE BREAKPOINTS"; to copy the slider positions of one timeslice to another, press the Control key while clicking on one of the buttons.
Once you've edited and MARKed at least two timeslices, you can connect the points between them into a continuous envelope by clicking on the SLICE 'N' DICE button. You can then view the new envelopes by selecting "All partials" under the Display menu. To generate a sample, you must set the pitch, duration, and sampling rate as before and select "Calculate" under the Sample menu.
Only timeslices that are MARKed will be treated as breakpoints in newly-created envelopes when you execute SLICE 'N' DICE. To remove a MARK from a timeslice, click on the UNMARK button.

And for the sample-impaired...

The final method of generating samples is also the easiest, since the program does most of the work. Select "QuikWave" from the Edit menu. Depending upon whether you're in amplitude or pitch envelope edit mode, a dialog box will offer several options that determine the shape and intensity of the envelopes you wish to create. A second dialog will ask for the range of envelopes to be generated. After generating the envelopes, you must set sample parameters as before and then generate the sample.

Hints

You can do lots of wild things with New Wave, and some will be ugly. Let experience be your guide. As a general rule, avoid drawing amplitude envelopes with steep slopes; a sudden shift in amplitude in the middle of a sine wave will cause a harsh-sounding glitch. You might want to refer to books on the acoustic properties of musical instruments to get an idea of how partials influence timbre. From there you can go on to experiment with irrational frequency ratios, sawtooth partials, and other debris from the sound-desingers lab.

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