JX-10 is a monophonic/polyphonic realtime VST-based synthesizer developed by Paul Kellet, and was ported to linux by David Robillard. It provides two oscillators (saw and pulsewidth) which can be isolated or blended. Polyphony is obtained using the glide control setting: zero for polyphonic, max for monophonic control. Standard ADSR envelopes are provided for timbre (filter) and amplitude. Pitchbend is set at one wholetone. The LFO depth is hardwired to the modulation wheel. I added a demo to give an idea of the very rich LP filter (last demo above).
Presets01 A few presets, to be decompressed in your .lv2 folder.
David Robillard's website