For those unfamiliar with Delia Derbyshire, she was one of the top pioneers of electronic music in the 1950s and 1960s. One of her best-known pieces was the original theme tune to Doctor Who. According to Wikipedia, "much of the Doctor Who theme was constructed by recording the individual notes from electronic sources one by one onto magnetic tape, cutting the tape with a razor blade to get individual notes on little pieces of tape a few centimetres long and sticking all the pieces of tape back together one by one to make up the tune".
Included in the finds was a piece of dance music recorded in the mid 60s, examined by contemporary artists, revealed that it would be considered better-quality mainstream today. Another piece was incidental music for a production of Hamlet.
The majority of her music mixed wholly electronic sounds, from a sophisticated set of tone generators and modulators, and electronically-altered natural sounds, such as could be made from gourds, lampshades and voices.