Source : Webster's Revised Unabridged Dictionary (1913)

Harmonizer \Har"mo*ni`zer\, n.
   One who harmonizes.

Source : WordNet®

harmonizer
     n 1: a musician who sings or plays in harmony [syn: {harmoniser}]
     2: a mediator who brings one thing into harmonious agreement
        with another [syn: {harmoniser}]