The Pro One's onboard sequencer, triggered by the TR-808's accent output, created electro's patterned basslines without MIDI

The Sequential Circuits Pro One was a monophonic synthesizer (essentially one voice of the Prophet-5) with an onboard step sequencer and an external trigger input. Electro producers discovered that routing the TR-808’s accent output to the Pro One’s trigger input would advance its sequencer in sync with the drum machine — years before MIDI existed. This created perfectly synced sequenced basslines tied to the drum pattern’s accent points. Newcleus used it on ‘Jam On It’; Juan Atkins used the same 808-triggers-Pro-One method on Cybotron’s ‘Clear.‘

Examples

Newcleus ‘Jam On It’: the bassline was programmed on one of the Pro One’s two 16-step sequences and triggered via the 808’s accent out. Cybotron ‘Clear’: the Pro One sequencer triggered from the 808’s trigger out.

Assessment

Explain the pre-MIDI synchronization technique: how did producers keep a drum machine and a synth sequencer in tempo sync? What physical connection made this work, and what is its modern DAW equivalent?