Helm

“Helm – a free, cross-platform, polyphonic synthesizer that runs on GNU/Linux, Mac, and Windows as a standalone program and as a LV2/VST/AU/AAX plugin.

It’s available now as beta release.

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

Helm is Free Software. You are free to run Helm anywhere, without the pains of DRM, you can study and change the source code and you can redistribute exact or modified copies of Helm.”

Source : tytel.org