Chris Sievey – Camouflage, 1983. This video shows a ZX81-program that runs in sync with the song. Sieve programmed the software as well. It available on the B-side of the 7″ vinyl, as a harsh audiostream of data. This audio could be loaded as software on the ZX81. More info.
Btw – the ZX81 turned 31 years old yesterday!