sight-transposition
The skill of reading music in one key while playing it in another, performed in real time without a written transposed part
In Depth
Sight-transposition is an essential skill for accompanists, who must often transpose songs to suit different singers, and for players of transposing instruments reading parts written for a different instrument. The performer mentally adjusts every note, accidental, and key signature while maintaining tempo and expression. Concert-level sight-transposition requires years of practice and is considered one of the most demanding cognitive feats in musical performance.
Gerald Moore, the legendary accompanist, could transpose any Schubert lied to any key at sight — a skill he considered the minimum requirement for a professional accompanist.