[sdiy] Polyphonic MIDI to CV

Brian Willoughby brianw at audiobanshee.com
Fri Jul 9 23:29:46 CEST 2021



On Jul 9, 2021, at 10:49, Rutger Vlek via Synth-diy <synth-diy at synth-diy.org> wrote:
> Interesting project! I have been playing with the same idea for a while. It's quite a challenge to replace keyboards with buss bars typically used in divide down architectures.

The nice thing about a CPU is that these complicated passive switches are not necessary. A CPU can decide to engage any number of analog switches on an incoming MIDI note message, without any complicated mechanicals.

> The range probably does not need to cover alle 128 midi notes, but at least the range of a stringer. A large array of quad VCAs (2164) could do the trick, but is rather costly. Via mcu you would be able to combine VCAs for multiple octaves on a single key (something normally done with multiple buss bars).

Forgive the naive question, but why would a stringer want multiple octaves on a single key? That's certainly understandable for an electronic organ - because it mimics the stops on an acoustic pipe organ - but stringers with full polyphony could simply engage notes individually, adding notes the the chord as necessary. Where organs are sine waves, and need overtones, stringers are ramp/sawtooth waves that already have harmonics.

Brian




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