Bounce

Transfer of several audio tracks to a new one (typically mono or stereo). It is an expression that originates from the days (1960s) when magnetic tape was the only tool for studio recording. The tape machines had limited tracks: two, four, and, if extreme, eight. If there were many instruments to record or voices to dub, a group of tracks were recorded, mixed down, and rerecorded on fewer tracks. For instance, four tracks were reduced to two, either on the same recorder or to another recorder (“ping-pong” recording). The instruments or voices were “bouncing” from track to track. Hence the name.