Rotate or randomise MIDI note on to different chains

[riban-bw]

Is your feature request related to a problem? Please describe.
It may be interesting to have a mode where each time a key is pressed on a MIDI keyboard, a different sound is played. This could be done by stepping through a set of chains either rotating through each in turn or randomly selecting a chain to play.

Describe the solution you'd like

• Additional modes for each MIDI input for chain-rotate and randomise (randomize).
• Parameters to set min/max chain or ability to select chains from a list or work on all chains with same MIDI channel.
• In these modes, each note-on command plays a note on the next chain in the selection.
• Previously played notes need to be remembered so they can be associated with the correct note-off.
• This could be done in the MIDI input options menu, alongside Multitimbral mode selection.

Describe alternatives you've considered
I wrote a LV2 plugin that provides this functionality based on MIDI channel switching but this does not work for all zynthian engines because many are omni channel.

Additional context
Other synths offer this feature, e.g. Korg Multi/Poly which allows to rotate through each of its 4 layers.