Tycho is free a spatial, cosmic, sci-fi oriented VST synth instrument, the emphasys is on expresiveness: velocity and aftertouch (no polyphonic aftertouch, alas) can do a lot to the sound, so try it with a full featured MIDI keyboard.
Short overview of the synth features:
O1, O2: 2 x double oscillators. each of the 4 operators can be sin, saw, ramp, triangle or square. the balance (crossfade) between the operators for each oscillator group can be affected by velocity (VEL), aftertouch (TOUCH), lfo (L1 -> O1, L2 -> O2). furthermore, the 2nd operator can be phase-shifted (SHIFT) in respect to the 1st. envelope is 6 stage. VEL>X specifies how much velocity affects attack phase (eg. before sustain): min is fixed EG, max is “higher velocity=faster EG”. VEL>Y controls velocity dynamics: min is no dynamics (same volume with every velocity), max is full dynamics (as usual). then there is a tuner for each oscillator group.
F1: filter (HP, BP, BR, LP, LP++, FEEDBACK). the last two are: 5 poles LP (rj_lpfilter3) and EVM’s feedback filter, don’t ask me how it works! cutoff (CUT) can be affected by velocity (VEL), aftertouch (TOUCH), lfo (L1, L2 or a crossfade between the two). it can also have an EG (also 6 stages). resonance (RESO) can be affected by aftertouch and lfo (see cutoff).
X1: effects (DELAY, FLANGER, CHORUS). with the lower knob (L/R SEP) at min, the filters are parallel. with the knob at max, filter 1 outputs on the left channel and filter2 on the right channel. you can also modulate the pan with lfo (L3, L4 or a crossfade between the two).
L1, L2, L3, L4: each lfo has 2 operators. the 1st (A) is plain sin, the 2nd (B) is sin phase modulated by A. the MIX knob controls if the lfo outputs only A (min), only B (max) or a crossfade between the two. operator B can be phase-shifted (SHIFT) in respect to operator A. if you enable SYNC, operator B will be hardsynced by operator A.
M1: main panel. mode can be POLY, MONO or UNISON. DETUNE is only effective in unison mode. GLIDE is your usual portamento, VOLUME is your usual volume.