[LAU] Yoshi/Zyn Instument envelopes

[Will Godfrey]

I've recently pinned down a number of oddities concerning these, and thought
what I've learned would be interesting to anyone working on their own
instrument patches.

The first thing to keep in mind is that amplitude envelopes (particularly
release time) set the point at which a note ceases. Frequency/filter envelopes
can be shorter, so their effect stops part way, but if they are longer, the
last part will be ineffective.

Across all three engines, and kits (if kit mode is active) it is whichever is
the longest that sets the overall time of the note, and you may well hear
others stop if the times are sufficiently different.

Also, within AddSynth itself, it is which ever voice has the longest envelope
that sets the overall voice time, and if you set voices with very different
characteristics you can hear the shorter ones finish before the overall sound
stops. Bear in mind, that each voice can also have a start delay set, so you
can get a late sound pickup that is then the last bit you hear, even if it's
quite short. However, if the start time of one voice is after all the others
others have finished it will never sound.

This sort of idea works best with 'Forced Release' disabled.

An unexpected twist to this, is that taking the combined voice envelope time
against the main AddSynth envelope, although attack and decay times follow the
above pattern, it is which ever has the *shortest* release that sets the
AddSynth time as a whole. This can really catch you out!

With regard to the Modulator amplitude envelopes. They don't change the overall
time, but if they are shorter than their voice length (or any voice that the
modulator is slaved to) the modulation may end a bit strangely. If they are
longer, then part of their action will be missed.

Finally, there is what I think is a bug (that goes back to Zyn 2.2.1). If an
AddSynth voice is enabled, it's amplitude envelope time is active, even if the
envelope is apparently deactivated and not editable. Oh, and by default all the
voice times are quite long, so again you could be puzzled as to why a sound is
longer than you expected. This has always been there, so I don't believe it
should be changed. To do so would quite likely alter many existing instrument
patches, but do keep it in mind.

In the latest Yoshimi commit, there is a new instrument in my 'Companion' bank
called 'AddSynth Morph' that demonstrates some of these points - I think it
sounds nice too :)

-- 
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.