***The developer's version has been suspended for the moment, and for now there's been a return to the last stable release, now 1:0.12.0+m1-6. The GUI is similar, but the presets posted previously have been removed due to incompatibility. I'm leaving the demos here to give an idea of this synth's performance capabilities.
Phasex, or Phase Harmonic Advanced Synthesis EXperiment, developed by William Weston, is a virtual synthesizer for the linux platform, and based on the concept of "phase offset modulation." The GUI above shows the entire panel, although it can be selected as two pages, with the oscillator section on the second page. It has both polyphonic and monophonic capabilities. It can be used as a plug-in or standalone.
There are 4 oscillators, each with a series of waveforms. External audio input (such as a second synth, or soundfont player, sampler, etc.) can also be routed as input, modulated through the envelopes, and reproduced as MIDI inputs are received.
All four oscillators, as well as four LFOs, can provide bipolar and unipolar output. Transposition, detuning and pitch bend can be set independently for each oscillator.
Both the amplitude and filter parameters are standard ADSR envelopes.
Chorus, delay and phased chorus effects are located in the lower lefthand area of the interface. Pan and stereo width controls are located on the left side of the GUI.
Ken Restivo's collection of patches for Phasex HERE. NB: Depending on the version you are using, these patches may or may not work.