The Collaborative International Dictionary of English v.0.48:

Disharmonious \Dis`har*mo"ni*ous\, a.
   Unharmonious; discordant. [Obs.] --Hallywell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disharmonious
    adj 1: lacking in harmony [syn: discordant, disharmonious,
           dissonant, inharmonic]