Vocal performances that are typically done as the rhythm instruments are being recorded so that the musicians can get a feel for the song and keep track of where they are in the tune. If the scratch vocals are recorded, they can contain leakage from other instruments, in which case they are usually deleted or erased. At times, the scratch vocals are so good they are kept as the main vocal tracks of the song.
SCRATCH VOCALS
Meaning of SCRATCH VOCALS in English
Guitar English glossary. Английский словарь гитарных терминов . 2012