A set of electronic-music production techniques which existed prior to the advent of synthesizers, as well as a facility where these techniques were utilized. Tape studios arose shortly after WWII, when the first practical tape recorders became available (the Nazis had invented the tape recorder's predecessor, the wire recorder, shortly before the war), and persisted until about 1980.
Tape studio techniques can be thought of as sampling before samplers were invented, and were an extension of the "musique concrete" movement of the early 20th century. Typically, tapes were made of sound samples, which might include almost anything, ranging from environmental sounds (rain, highway traffic, backround conversation) to found objects which were hit/plucked/bowed etc., to electronic laboratory instruments of the day. The tapes then might be played at various speeds onto another tape, creating a range of pitches. Then, the different sound tapes would be cut into pieces, and the mixed pieces hand-spliced into new tapes which were mixed and overlaid. Careful editing of the tapes could produce electronic-sounding but surprisingly recognizable melodies and rhythms (as the BBC Radiophonic Workshop often did for its television program scores). Of course, the technique was also used for a wide variety of more experimental music.
Tape studios fell out of favor in the 1980s as samplers which could do the job with far less trouble became more affordable.