amsynth 
Analog Modelling SYNTH for Linux - LV2 | DSSI | JACK | ALSA | OSS
- Dual oscillators (sine / saw / square / noise) with hard sync
- 12/24 dB/oct resonant filter (low-pass / high-pass / band-pass / notch)
- Mono / poly / legato keyboard modes
- Dual ADSR envelope generators (filter & amplitude)
- LFO which can modulate the oscillators, filter, and amplitude
- Distortion and reverb
- Hundreds of presets