Following on from the release of The Kit and the Music Percussion Computer (MPC-1) in 1982-1983, Cambridge company MPC Electronics released the excellent-sounding drum synthesizer section of the MPC-1 as DSMs - Drum Synthesizer Modules - in 1984. The first two releases encompassed the DSM1 with one drum sound section and a section holding the master power unit for several modules, and the DSM2 that connected up to the DSM1 and featured two drum sound sections. MPC Electronics provided two different designs of electronic drum pad triggers to accompany the DSM racks, each available in variety of colourful shells. 1985 saw the DSM8+ (Auto Tom) release, a single voice module with a programmable run generator variable in number of steps and number of beats to provide a selection of tom-tom drum rolls in increasing or decreasing pitch using just a single electronic drum pad. The DSM32x4 rack was a programmable single voice module with sound generation that included FM-type modulation, and up to 128 user programmable patch locations stored in the rack's memory. This operating manual provides - for the first time - a guide to operate all four released DSM racks, packed with photographs and additional sourced information to enable the user to get the best out of their vintage drum synths. As an additional bonus, the manual also includes a comprehensive history of MPC Electronics featuring all the company's releases designed by the innovative Clive Button from the introduction of The Kit in 1982 through to the end of the company in 1986.