helm

Developer Matt Tytel has introduced Helm – a free, cross-platform, polyphonic synthesizer that runs on GNU/Linux, Mac, and Windows as a standalone program and as a VST/AU plugin.

Features:
32 voice polyphony
Interactive visual interface
Powerful modulation system with live visual feedback
Dual oscillators with cross modulation and up to 15 oscillators each
Unison and Harmony mode for oscillators
Oscillator feedback and saturation for waveshaping
12 different waveforms
7 filter types with keytracking
2 monophonic and 1 polyphonic LFO
Step sequencer
Lots of modulation sources including polyphonic aftertouch
Simple arpeggiator
Effects: Formant filter, stutter, delay