Keypad poly 3 & keypad polyest — “polyphonic” synths using one keyboard module

Both of these are fairly basic synthesizers: Keypad poly 3 is a 6-voice, triangle-based synth with FM feedback and duty cycle modulation, fed into a reverb lite. Keypad polyest is an 11-voice sawtooth-based synth, also fed into a reverb lite. The names derive from an earlier iteration of “polyphonic” keyboard module synths I did:

The big news here is the use of a single keyboard module to produce the “polyphony.” (Although I like keypad poly 3 and I hope you will, too; keypad polyest is really more of an experiment than a finished product, in my eyes.)

I will present the “recipe” in the Tips & Tricks page, but the basic idea is: the trigger output of the keyboard module fires each time a new note is selected. We can use this output to gate a sequencer (I use an AHD envelope and a comparator between the two to produce the desired outcome). This sequencer then distributes, via CV out switches, note values to sample and holds (which in turn feed the oscillators) and triggers to ADSRs (set to attack/decay, with immediate release off, so they complete their cycle once triggered). The triggers are also distributed to the trigger inputs of the sample and holds.

It is the use of triggered envelopes that makes this only “polyphonic” to me: while there are several oscillators being heard at the same time, there is no way to individually gate the oscillators, which limits the individual articulation of each voice.

There is technically a gap between each note of a couple milliseconds, but you would be hard-pressed to recognize it. (I can’t.) Press down on four notes at once, heard four notes at once, etc.

Both patches output in stereo, although only Keypad poly 3 makes use of the stereo field (both outputs of Keypad polyest are exact copies of one another).

Tips and Tricks page:


(The keypad polyest is a much simpler synth; some controls overlap between the two patches, but I will designate those which are exclusive to Keypad poly 3 with a * asterisk):

The first page is a keyboard module, tuned to A minor, with each row representing an octave. You can retune it to whatever you like, or, if you would like to play in another minor scale/shift octaves, there is a “Transpose” control on the second page.

Transpose — change the keyboard module to another key (e.g. set to C1 for C minor) or change the octave range (e.g. set to =A1 to bring the range down an octave)

Attack and decay — control the attack and decay stages of the envelopes

FM amount* — controls how much each oscillator is fed back into itself; above ~.6000, noise will begin to be introduced as the feedback clips

Duty cycle* — sets the duty position of the oscillator; .5000 is a symmetric triangle wave

Duty mod depth* — depth of the duty cycle modulation (sine wave LFO)

Duty mod rate* — rate of the duty cycle modulation (sine wave LFO); at low speeds, this has an almost vibrato-ish effect, as the rate is increased, the effect becomes more like a second source of FM, distorting the waveform and changing the timbre

Voice spread* — pans the voices across the stereo field

Reverb decay — controls the reverb decay

Reverb mix — controls the reverb mix

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