Princeton's WordNet

1. harmonize, harmonise, consort, accord, concord, fit in, agree(verb)

   go together

   Synonyms:
   assort, harmonize, grant, accord, consort, gibe, fit, fit in, hold, agree, check, affiliate, match, concord, run, tally, correspond, jibe, associate, reconcile, chord, allot, harmonise, concur

2. harmonize, harmonise(verb)

   write a harmony for

   Synonyms:
   harmonise, fit in, agree, consort, reconcile, harmonize, concord, chord, accord

3. harmonize, harmonise(verb)

   sing or play in harmony

   Synonyms:
   harmonise, fit in, agree, consort, reconcile, harmonize, concord, chord, accord

4. harmonize, harmonise(verb)

   bring (several things) into consonance or relate harmoniously

   Synonyms:
   harmonise, fit in, agree, consort, reconcile, harmonize, concord, chord, accord

5. harmonize, harmonise, reconcile(verb)

   bring into consonance or accord

   Synonyms:
   harmonise, fit in, settle, agree, accommodate, consort, submit, resign, reconcile, make up, harmonize, concord, chord, patch up, accord, conciliate

6. harmonize, harmonise, chord(verb)

   bring into consonance, harmony, or accord while making music or singing

   Synonyms:
   harmonise, fit in, agree, consort, reconcile, harmonize, concord, chord, accord