By February 1992, Music Technology had reviewed the Alesis D4 as a one-rack-unit drum module. Its design placed a large sampled percussion library and a trigger-to-MIDI interface in the same box, while deliberately leaving sequencing to an external musician, sequencer or drum machine.
The evidence, in view
Drums waiting for a gesture.
The contemporary review shows the D4 as it met players: a shallow rack unit built around a 501-sound library and the ways a drummer or sequencer could reach it. This is a February 1992 review image—not a claim about first release or original worldwide price.
Source (1)
A drum machine without the drum machine part
A drummer could connect pads or acoustic-drum pickups to the D4 and play its sampled percussion from the kit. MIDI notes offered another route into the same sounds. The one-rack-unit module left sequencing outside the box: it supplied the drums while a player, drum machine or sequencer supplied their timing.
Five hundred and one voices
Inside were 501 drum, percussion and effect samples, with 16-note polyphony. Four audio outputs let parts of the kit take separate paths to a mixer. A two-line display, data wheel and editing keys kept the sound assignments on the front panel; the Preview button allowed a sound to be auditioned there.
The trigger interface
The twelve trigger inputs were the practical connection between the rack and a performance. Tim Goodyer’s February 1992 review described pads, piezo-equipped acoustic drums and signals recorded on tape as possible sources. Recorded drum hits could call up replacement sounds, and the trigger interface could send MIDI to other equipment. The D4 could join an existing kit or recording setup without taking over its clock.
Source
The visual archive