Accompanist n. : The performer in music who takes the accompanying part.

Example:
How do you prepare for a concert as a piano Accompanist?

Taxonomy
accompaniment, accompanist, music, free encyclopedia, melody, instruments, typical accompaniment, accompaniment figure, pitches, van der Merwe, musician, play the melody, music accompaniment, search, pattern, Mozart, concert, aria.

Defination from the web:
accompanist is one who plays an accompaniment. ... In some American schools, the title collaborative pianist (or collaborative artist) is replacing the title accompanist. ... The term accompanist is also used to refer to a musician (generally pianist) who will not necessarily be ...