I could not reply to the thread because for some reason this email never showed up on my mail box (I only saw it at the listserver).
But here’s my thoughts.

- it may be possible to design a way to have single-instance monophonic synths but I think the question appears
to mix up instantiation with opcode behaviour (e.g. envelopes) in such a way that needs to be disentagled.

- It is likely possible to meet the envelope requirements in the ticket by taking a step back and looking at how
they are implemented. For example, we could design an envelope that is dependent
on a gate signal, an instrument that models the VCA and an instrument that would 
manage this gate signal to play the VCA. It doesn’t meet the requirements of a single instrument, but models
the mono synth.

- the solutions for i-time and k-time opcodes may also be implemented but they would need one instrument
that is constantly running to keep track of things. Iain’s single instrument solution uses global memory to
keep track of voices, but it has some shortcomings in terms of the release assumptions (as you discovered).

I’ll see if I can sketch a minimal example of the gate signal idea.
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Prof. Victor Lazzarini
Maynooth University
Ireland