Overdubbing

Overdubbing is a technique used by recording studios to add a supplementary recorded sound to a previously recorded performance.

Overdubs can be made for a variety of reasons. One of the most obvious is for convenience; for example, if a bass guitarist is temporarily unavailable, the recording can be made and the bass track added later. Similarly, if only one or two guitarists are available, but a song calls for multiple guitar parts, a guitarist can play both lead and rhythm guitar