accompaniment
n//əˈkʌm.pə.ni.mənt//ackompanjemang, komp, tillbehör
(music) A part, usually performed by instruments, that gives support or adds to the background in music, or adds for ornamentation; also, the harmony of a figured bass.
That which accompanies; something that attends as a circumstance, or which is added to give greater completeness to the principal thing, or by way of ornament, or for the sake of symmetry.