Yamaha SY35
Vector Synthesizer
Yamaha SY35
click to enlarge

This the cheapest synth I ever had, got it of gumtree for 45 quid, but there is few faults with it.
3 Keys are not working and the contact board is cracked (just got new one of ebay :)), so only midi control at the moment.
here is few words about the unit from Vintage synth explorer.
The Yamaha SY35 is a bit unique in that it is a Vector Synthesis system, combining FM and AWM sample playback voices to create sounds suitable for virtually all kinds of music. It features significantly expanded memory capabilities over the SY-22. It has an extremely large database of over 128 AWM sampled sounds (you cannot add more) and around 256 FM waves. Waves and samples are combined and edited with a roller/joystick (the vector wheel). At a time when Yamaha was making the switch from FM synthesis, which ruled their synths of the eighties, to AWM and AWM2 synthesis in the nineties, the SY-35 represents a model that was on the cusp, having one foot (or pair of oscillators actually) in each world.

Editor for the Yamaha SY22, SY35 and TG33
Click me
Atmospheric pad modulated by the vector joystick
Rhythmic onboard wave and noisey sound on opposite vectors
Multi patches (fat, wide and atmospheric pads and fx)
WOW there are also cool drum sounds on board, here is an example + few of the effects