Polymeter 0.0.29 adds Chord Modulation and mapping to steps

Polymeter 0.0.29 introduces a major new feature called Chord Modulation, explained below. There are many other additions and improvements, including the ability to remotely control each individual step of a track. The release notes are here.

Chord Modulation

A scale is a subset of the chromatic scale. Each scale tone is a note, expressed as an offset in semitones relative to some base note. Assuming a base note of C, zero is C, one is Db, two is D, three is Eb, and so forth.

A chord is a subset of a scale. A chord can contain any number of tones, up to and including all of the tones of the parent scale. Chords are created by modulating a note track with a combination of scale, chord, and index modulators. Voicing modulators may optionally be added also.

Without a chord, index modulation accesses the tones of the current scale. The index modulation picks a scale tone, and the scale tone maps to a note. For example, suppose a note track has seven scale modulators, constituting a C major scale: C, D, E, F, G, A, B. The index modulation is interpreted as a zero-based index into that scale, ranging from zero to six. In other words, if the index modulation is zero the C is picked, if it’s one the D is picked, if it’s two the E is picked, and so on.

With a chord, index modulation accesses the tones of the current chord. This adds an extra level of mapping. The index modulation picks a chord tone, the chord tone map to a scale tone, and the scale tone maps to a note. Suppose the track has four chord modulators, which output 0, 2, 4, and 6 respectively. These correspond to the first, third, fifth, and seventh notes of the current scale. So if the scale is C major as before, the resulting chord is C major seventh.

Pitches:

Index	0	1	2	3	4	5	6	7	8	9	10	11
Note	C	Db	D	Eb	E	F	Gb	G	Ab	A	Bb	B

Scale:

Index	0	1	2	3	4	5	6
Scale Tone	0	2	4	5	7	9	11
Note	C	D	E	F	G	A	B

Chord:

Index	0	1	2	3
Chord Tone	0	2	4	6
Scale Tone	0	4	7	11
Note	C	E	G	B

In this example, when accessing the scale, indices 0, 1, 2 map to the notes C, D, E but when accessing the chord, the same indices map to the notes C E G. The chord gives the indices a different meaning.

Notice that three things are being distinguished: the subset of notes (the scale), the subset of scale tones (the chord), and which tone is picked (the index). All three of these entities are distinguished from the rhythm, which is determined by the note track. So we have an orthogonal system in which each axis (scale, chord, ordering, and rhythm) is independent of the others.

A demo file that makes use of chord modulation is attached to this post. The demo file uses chord modulation to implement the "Numbers" system of tonal palettes popularized by my ex-teacher, noted tenor saxophonist Jerry Bergonzi. This system was also implemented in my previous project ChordEase. The Numbers system is explained here.

Mapping to Track Steps

Why would you want to want to map a controller to a track step? I’m glad you asked that question. For one thing, it means you can control the tempo. Here’s how.

Create a track, change its type to Tempo, set its Length to one, and set its Duration to 100. The duration in this case is repurposed as the range of tempo scaling, as a percentage. The 100 means the tempo control ranges from half time to double time. Create a mapping for whatever controller you’re using. Within the mapping, set the Output Event to Step, the Output Control to zero, and the Track to your tempo track. Note that for Step mapping, Output Control is the zero-based index of the target step.

Start the sequencer. Your controller should now control the tempo. Zero gives you half time, 127 gives you double time, and at 64 the base tempo is unaffected.

There’s lots of other fun stuff you can do with step mapping. For example, you could make an empty track, and then map each of its steps to a key on a keyboard. Pressing and holding a note on the keyboard sets the corresponding step in your pattern. How hard you hit the key determines the step’s velocity. Playing a chord on the keyboard gives you a rhythm.
Try doing this for two different tracks, each with a different prime length. For example one could have a length of five and the other a length of seven. Create two sets of step mappings, one for each track, on different ranges of the keyboard. Now you can dynamically create two rhythms, one with each hand, and they’re in polymeter. Pretty cool!

Step mapping will most likely be useful for controlling the behavior modulator tracks, for example range modulation, voicing modulation, and so on.