Solidac Experimental Computer

The Solidac Experimental Computer was built between 1958 and 1963 as Scotland’s first solid-state minicomputer. It was developed at the University of Glasgow by Paul Anthony Vincent Thomas in collaboration with Barr & Stroud Ltd., a Glasgow firm recognized for its precision optical instruments, including binoculars, submarine periscopes, and naval rangefinders. Compact enough to fit within a desk console, it combined a 20-bit word length with 1,024 words of magnetic-core memory and a distinctive system of pivoting circuit “leaves” that made its internal design visible and accessible. Conceived as a teaching computer, Solidac was later used at Glasgow to give students direct experience with machine-language programming. Among those who worked most closely with the machine was Barr & Stroud mathematician Thomas H. O’Beirne, who extended its use beyond the classroom into the field of experimental music. In 1965 he gave a public lecture titled Music, Numbers, and Computers, concluding with a live demonstration of Solidac in which audience members were invited to enter numbers on its console using a rotary telephone dial.

In 1967 O’Beirne directed Solidac to perform Mozart’s Musikalisches Würfelspiel, the eighteenth-century dice game in which pre-written musical measures were assembled according to chance. Programmed at the machine-code level, the computer generated entire sequences of waltzes and contredanses, rendered as bright reed-like tones produced by rectangular electronic pulses. The resulting LP, A Small Computer Plays Some Samples of Mozart’s Dice-Composition Music, was one of the first commercial records of computer-produced music. O’Beirne later developed the ORPHEUS programs, which expanded Solidac’s capabilities to microtonal scales and even the timbre of the bagpipe, positioning the machine as a performer able to interpret both classical works and Scottish folk music. Returning to Glasgow’s Department of Computing Science in 1969, Solidac was used to teach assembly language into the 1970s before retirement. Today it is preserved in the National Museums Scotland collection.