This is a vintage Korg synth jam featuring:Korg MS-50, MS-20, MS-20 and SQ-10.

via Newueel:

Another interesting experiment with only original live created MS-20 / MS-50 sounds (incl. beat), no FX at all!

The SQ-10 triggers and sequences all synths:

• The MS-50 plays a rythmic bass pattern (SQ-10 channel A+B).
• The MS-20 plays another rythmic pattern using 2 different tuned VCO’s, also sequenced by channel A+B, but using the inverted signal, which also goes through the MS-50 integrator for portamento purposes. EG1 controls the VCO frequency and swaps between 2 CV values every 32(!) steps, by using step 1 trigger output (which triggers once every 8 steps) divided by 4 (MS-50 divider) to generate a trigger once every 32 steps.
• The other MS-20 plays a simple beat, a bass drum with hi-hat pattern (channel C).