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Synonyms for Accompaniment (same or very similar meaning)

WordNet sense 1 (an event or situation that happens at the same time as or in connection with another):
attendant, concomitant, co-occurrence

WordNet sense 2 (a subordinate musical part; provides background for more important parts):
backup, support, musical accompaniment

WordNet sense 3 (the act of accompanying someone or something in order to protect them):
escort, escort

From the ODE community, based on WordNetadd/edit