The Collaborative International Dictionary of English v.0.48:
Harmonizer \Har"mo*ni`zer\ (-n[imac]`z[~e]r), n. One who harmonizes. [1913 Webster]WordNet (r) 3.0 (2006):
harmonizer n 1: a musician who sings or plays in harmony [syn: harmonizer, harmoniser] 2: a mediator who brings one thing into harmonious agreement with another [syn: harmonizer, harmoniser]