hexter To-Do list, in no particular order:
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* Clean up all "!FIX!"es (and "-FIX-"es).

* Optionally sort patch list alphabetically (Steve Harris).

* implement amplitude modulation, LFOs, and mod source routing (mod
    wheel, breath controller, foot pedal).

* optimize so if a voice just being set up still has all the
    patch data for the current edit buffer, we skip loading it.

* Figure out the feedback scaling "fudge factor".  The current 0.18
    is close, but not right on.

* Finish pitch envelope time calculation stuff.

* Add a high-pass filter to the output, to block very low frequency
    output like the DX7 does.

* Implement de-clicking of stolen voices.