vintage analog analogue modular synthesizer drumcomputer repair reparatie modification modificatie midification MIDI crumar yamaha cs roland mks juno jupiter sh tb tr korg ps ms moog prodigy memorymoog rogue source minimoog bit sequential circuits prophet oberheim ob matrix ppg wave teisco arp doepfer elka synthex siel opera rhodes chroma jen solina osc oscar edp wasp akai ems emu octave cat linndrum