noun (n)

• an event or situation that happens at the same time as or in connection with another(noun.event)

  Synonym:
  attendant, co-occurrence, concomitant
  

  source: wordnet30
• a musical part (vocal or instrumental) that supports or provides background for other musical parts(noun.communication)

  Synonym:
  backup, musical accompaniment, support
  

  source: wordnet30
• something added to complete or embellish or make perfect(noun.attribute)

  Example:
  Wild rice was served as an accompaniment to the main dish.
  

  Synonym:
  complement
  

  source: wordnet30
• the act of accompanying someone or something in order to protect them(noun.act)

  Synonym:
  escort
  

  source: wordnet30
• 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.(noun)

  source: webster1913