From French accompagnement; equivalent to accompany +‎ -ment. First attested in 1744.

• enPR: ə-kŭmʹpə-nē-mənt, IPA^(key): /əˈkʌm.pə.ni.mənt/, /əˈkʌmp.ni.mənt/

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accompaniment (countable and uncountable, plural accompaniments)

1. (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.

   Synonym: comping

   Brooks performed a saxophone solo on stage, with Robert as accompaniment on the bass.

2. 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.

   Synonyms: attachment, supplement; see also Thesaurus:adjunct

   A side salad is a common accompaniment to a main dish.

   forecasting torrential rain, with an accompaniment of crashing thunder.

   Green sauce is the perfect accompaniment to baked fish.

   • 1952 February, H. C. Casserley, “Permanent Wayfarings”, in Railway Magazine, page 77:

     My audience to this not-too-easy operation was a small group of Scottish school lasses, who seemed (perhaps naturally) to find the proceedings somewhat mysterious, but at any rate amusing. I wished they would go away, but they didn't, so I had to get on with the job to the accompaniment of a background of giggles!