Kawai K5m

Back in 1987, this rackmount module brought additive synthesis to bedroom studios and pro racks at a price that didn't break the bank, letting anyone stack up to 126 sine wave harmonics for sounds no subtractive synth could touch.

Its hybrid engine shines in full mode with all 126 harmonics in series or twin mode splitting two detunable sets of 63, each assignable to one of four 6-stage envelopes for amplitude shaping, plus dedicated 6-stage envelopes for pitch, a resonant lowpass digital filter, and 7-stage amp. A single LFO with saw, triangle, square, and other waves modulates via velocity, aftertouch, or MIDI, while 16-voice polyphony handles 15-part multitimbral setups across four individual outs plus stereo mix. MIDI In/Out/Thru, sustain pedal, and 48 internal patches (expandable via card) make it studio-ready, all in a compact 4U chassis at 4.8kg.

Players dig its expressive response to velocity and pressure for organic feels from digital bones, and those bar-graph displays make harmonic tweaking visual and fun, though programming takes patience away from analog habits. Jan Hammer tapped it for its thick, evolving textures that still cut through mixes today.