I'm building an open source FM synth in VST/AU form with Juce. I've just implemented a simple glide option when numVoices gets set to 1 (it's an option in the GUI of the plugin). There's one nasty side effect somehow, to Synthesiser's handling of voices. The envelopes retrigger (which I believe I want to have), and they make the sound crackle when going from one note to another, while the first one is held down. The other, less annoying thing is that when key A is held down, then key B is held down and released again, the sound is not returned to the first pushed key.
Does anybody know of (re)implementations of Synthesiser, or perhaps workarounds, that are open source and have already made this to work?