With the advent in the late 1940s of acetate-backed magnetic tape on which to record sound, a new approach to the composition of music began to develop. Recorded sounds could now be altered by cutting tape and re-attaching it in different configurations. Sounds could be layered, played backwards, electronically altered, and then re-recorded. Compositions were produced using these techniques, and then played over speaker systems in concert halls, often without the involvement of performers. The setting for this compositional activity, resembling a laboratory because of the large amount of electronic equipment, became known as the electronic music studio.

There were two trends in this music in the 1950s: electronic music, in which sounds were generated by electronic devices such as oscillators, predominated in Germany, while musique "concrète," which used sounds recorded on tape by microphones, predominated in France. Composers in both styles adapted the sounds for various contexts, using remarkably similar means, such as reverberation, mixing, changed playback speeds, and filtering. The end result, however, was always pre-recorded, and the music became known as "tape" music. In North America, composers tended to combine both methods.

Composers Istvan Anhalt (left) and Paul Pedersen (right) worked with newly designed instruments at the McGill University Electronic Music Studio. (National Library)