WhySynth is a versatile softsynth which operates as a plugin for the
Disposable Soft Synth Interface (DSSI).  A brief list of features:

- 4 oscillators, 2 filters, 3 LFOs, and 5 envelope generators per
  voice.

- 11 oscillator modes: minBLEP, wavecycle, chorused wavecycle,
  asynchronous granular, three FM modes, waveshaper, noise,
  PADsynth, and phase distortion.

- 10 filter modes.

- flexible modulation and mixdown options, plus effects.

WWW: http://smbolton.com/whysynth.html