MIDI Clock sends 24 pulses per quarter note so slaved devices can synchronise tempo to a master sequencer

MIDI Clock is a system real-time message transmitted 24 times per quarter note (PPQ) by a master device such as a sequencer, drum machine, or DAW. Slaved devices (synthesizers, loopers, effects) use the stream of clock pulses to derive the current tempo: 24 pulses per beat at 120 BPM = 48 pulses per second ≈ one pulse every 20.8 ms. Tempo changes are automatic—the master speeds up or slows down the clock rate, and all slaves follow. MIDI Start, Stop, and Continue messages trigger playback coordination. While adequate for most musical uses, MIDI Clock has jitter (timing inconsistency) at the millisecond level; tighter synchronisation of digital devices requires SMPTE timecode or word clock.

Examples

A drum machine (master) at 128 BPM sends 24 × 128/60 ≈ 51.2 MIDI Clock messages per second. A synthesizer arpeggiator (slave) divides these pulses to generate notes at the correct rhythmic subdivision. In Ableton Live, enabling MIDI clock output to hardware synths synchronises their arpeggiators to the project tempo.

Assessment

A sequencer is running at 90 BPM. Calculate how many MIDI Clock messages per second it transmits. Then describe what happens to a slaved arpeggiator when the master tempo increases to 120 BPM.