I've made a small change to [polywavesynth] that ensures that preset volumes only change for new notes. Previously, switching to a new preset could cause a volume discontinuity in an already-triggered note.
I've been testing this version (2.3) a great deal, and it seems very satisfactory.
Download it at http://www.pkstonemusic.com/code/polywavesynth.tgz .
See http://www.pkstonemusic.com/polyWaveSynth.html for more info on [polywavesynth].
Phil Stone pkstonemusic.com