Source : Webster's Revised Unabridged Dictionary (1913)

Accompaniment \Ac*com"pa*ni*ment\ (-ment), n. [F.
   accompagnement.]
   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. Specifically: (Mus.) A part performed by
   instruments, accompanying another part or parts performed by
   voices; the subordinate part, or parts, accompanying the
   voice or a principal instrument; also, the harmony of a
   figured bass. --P. Cyc.

Source : WordNet®

accompaniment
     n 1: an event or situation that happens at the same time as or in
          connection with another [syn: {concomitant}, {co-occurrence}]
     2: a subordinate musical part; provides background for more
        important parts [syn: {musical accompaniment}, {backup}, {support}]
     3: the act of accompanying someone or something in order to
        protect them [syn: {escort}]