PolyMux and Sustain

I’m intrigued by the possibility of using my Syntakt as a polyphonic synth using something like the Retrokits RK-002 for voice allocation. Does the PolyMux algorithm do anything with sustain pedal info and other CC messages? I would imagine you’d want them broadcast to all active channels. Also, what are good alternatives to the RK-002 (including things that would run on a Raspberry Pi, iPad or Mac?

Drambo on iPad has a Mono to Poly midi module, but as far as I can tell it is locked to 4 voices (you can’t do just 3, which is how I’d want to combine 3 analog machines, or in general triads on a digital machine).

My new RK-002 is also locked to 4 machines because I don’t have a MIDI interface that can successfully update the firmware to it.

I’m commenting to listen for other answers, too, because I also have a spare raspberry pi sitting around that I’d like to make a 3 channel polyphonic script for, but haven’t had luck finding a good starting point for it…

I wonder if Sonic Pi or TidalCycles would be appropriate. What’s the firmware update issue? MIDI power?

I haven’t tried it yet, but there’s a MIDI scripting iOS app called Mozaic and this script for it

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Thanks for these leads on other mono to poly solutions! I assumed that it’s a problem that has been solved many times

I haven’t extensively trouble…shot(?) it, but the RK-002 is either not getting power or not receiving sysex messages with improvised setups involving a usb-midi cable and different devices’ MIDI thru ports.

I was able to answer your initial question, though, and was pleasantly surprised to see: sustain via cc 64 works great, and voice stealing is fine too. (Had to edit down to upload directly)

And to confirm this is the RK-002. Also tested with the ST midi LFO sent to the 4 tracks’ filter, and it worked very smoothly, so I’d assume it’s sending cc to all connected channels. I bet @sezare56 would know for sure (and has some nice demos of ST and RK 002 in other threads on polyphony).


Check out Midihub or MidiGAL

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Cool. Thanks.


I have a Midipal, which can be used standalone. But as it require extra power (or 9v) I prefer to use RK002. I use “Polymux Example with Aftertouch” script.
Held notes are kept, and it can send all CCs to all poly channels.

Reporting back here I was able to adjust the RK-002 number of polyphony channels by using channel 9 program change messages. It wasn’t clear this was possible in the setup, as T he instructions were a little gnomic, and well hidden to boot, but I found a nice post from this summer that explains the midi PC and CC implementation: Digitakt RK-002 set-up and use issue - #2 by iotb

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Check the script on DUY page. There are other usefull commands.

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In iOS land, Polythemus does this trick well with a decent amount of flexibility (as an AUv3 MIDI effect, so it needs a host like AUM ).


Thanks! I was not aware of this one. Just tried it within AUM (without external gear). The links on app store go to a weird Japanese page or to a Facebook page for MIDISequencer, but I’ll check it out.

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Yep, it’s legit, has worked for me with Digitakt and Nord Drums. Same dev as Quantum, a wild and unique sequencer, worth a look.

Edit: solved

@handed Wondering if you can help me with the setup. This old video shows a place to set the MIDI channel of each voice, but my version of Polythemus doesn’t seem to have that icon. I have a mioXC USB->MIDI cable and routed all the outputs of Polythemus to that (in the AUM matrix). But all of my Polythemus outputs are labelled "@M3:1 Polythemus " where n is 1,2,3. AUM is talking to the Syntakt but only on channel 1.

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Solved. I found the link to manuals on the Midisequencer Facebook page.
Up and running now.


Just saw your post - glad you got it solved! Think I might have another go with it soon to play my Nord Drum 2 polyphonically.

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