A backing track is an audio or MIDI recording that musicians play or sing along to in order to add parts to their music which would be impractical to perform live. Bands or solo musicians may use backing tracks to add extra instrumental or vocal tracks to a live performance, to enhance the sound (as in the employment of doubled backing vocals) or to replicate more closely the instrumentation on record (as in the use of additional recorded parts such as string sections.) A singer or vocal group performing without a band may sing along to pre-recorded music.