harmonist

Short definition from Wiktionary

Noun

1. 1
   One who shows the agreement of corresponding passages of different authors, as of the four Biblical evangelists.
2. 2
   One who understands the principles of harmony or is skillful in applying them in composition; a composer.
3. 3
   A member of the Harmony Society, a Christian theosophy and pietist society founded in Germany in 1785.