The Doctor Rhythm DR-110 Graphic is a drum machine introduced in 1983 by the Boss product division of the Japanese Roland Corporation. It was the second entry in their DR series, following up on the much simpler DR-55. History Boss were better known for producing electric guitar accessories such as effects pedals, and the DR-110 is similarly small and lightweight in size (190×110×30mm, and only 450g), and like most Boss equipment, could be run from a 9V d.c. supply [negative centre] or batteries. Although not designed as a high-end studio product, The DR-110 nonetheless featured some noticeable advances in technology compared to previous Roland drum machines. It has an LCD graphic display, showing a step-programming grid for the various drum voices. Rubberized touchpads each represent one of the DR-110 voices, and can be used to build a pattern in realtime as well as to enter and edit note data. The DR-110's synthesized drum "voices" (synthesizer sounds) use analog synthesizer circuits. Tempo is continuously variable between 45 and 300 bpm. The DR-110 used a four-bit Hitachi HD44790A44 CMOS microprocessor and 0,5 KB of μPD444C RAM memory. In 1985, Boss released the smaller DR-220 with eleven voices. These devices had much the same functionality as the DR-110, but relied upon digital button-press control of parameters rather than knobs. Drum sounds The DR-110's six synthesized drum voices were: bass drum snare drum open hi hat closed hi hat hand clap cymbal As with most previous Roland drum machines, the bass and snare voices are generated by a "damped tuned resonance" oscillators. The cymbals and hi-hats are created by VCA-shaping and band-pass filtering a combination of white noise and four non-harmonically related square wave oscillators (generating a much more realistic sound than white noise alone). The clap sound uses only shaped white noise, but was triggered by a multiple pulse train, to create a reverberation effect. No tonal variation of the voices is possible; however (as with several earlier Roland drum machines), the relative balance is variable between the bass and snare drums versus the hi-hat and cymbal. An accent (volume increase) can also be added on any pattern step; the amount of accent is globally variable with a knob. Rhythm patterns The DR-110 offers 16 preset patterns, and 16 memory locations for the user-created patterns. Each pattern can be divided into 16 or 12 steps. The DR-110 also has two "song" memories, each