Siel MDP-40

Forty rhythms in a little plastic box

The MDP-40 looks like an accompaniment machine made for the moment when MIDI was becoming ordinary: a light, compact unit with 40 preset rhythms, a line of playing buttons and a handful of practical ways to get from one section to the next. Its manual calls the model MDP 40; the circuit drawings also carry the Suzuki RPM-40 name, preserving a real shared design rather than a speculative resemblance.

A verse, a chorus, then a break

The forty rhythms are arranged as twenty verse-and-chorus pairs. Swing, clap addition, intro and break controls gave the panel a small vocabulary for making a preset accompaniment change shape in time. Manual Drum turns the same buttons into direct instrument triggers, while tap and numeric tempo entry make the little box unusually easy to steer without an external sequencer.

MIDI at the edges

The MDP-40 could also take an external clock and respond to MIDI. Ten ordinary drum sounds were mapped alongside low snare, bass drum and hi-hat variants that appear only through MIDI notes. There is no pattern memory to fill or sampling input to exploit; the interest lies in a fixed sound set made more useful by external control.

One circuit, several badges

The schematic names the MDP-40 and RPM-40 together and identifies its processor, memory and control matrix. A later Keytek owner remembered using MIDI when aging front-panel switches became temperamental, a reminder that small rhythm machines often survive as individual working objects rather than as a single uniform production run. The shared circuit record gives the badges their family connection; the individual panel still tells each machine’s own story.

A small Italian rhythm box in a toy-strewn record

The MDP-40 turns up in the official credits for The Pleasure Class’s 2016 Sensual Passport, where Dan Nelson lists it beside a TR-606, a Yamaha CS-5 and a Prophet V. It is exactly the kind of context that suits the machine: a modest preset box joining an intentionally eccentric orchestra of small instruments, percussion and home-studio choices.

On record

• Dan Nelson / The Pleasure Class — Sensual Passport. The official Sensual Passport credits name Dan Nelson playing a SIEL MDP-40 drum machine. Source ↗

In the studio and on stage

• FotoCrime — House of Foto studio practice. FotoCrime lists a SIEL MPD-40 among the rhythm machines in its recording studio. Source ↗