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]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "disharmonious":
   absonant, antagonistic, antipathetic, at cross-purposes,
   at loggerheads, at odds, at variance, at war, atonal, cacophonic,
   cacophonous, clashing, colliding, conflicting, contradictory,
   contrary, cracked, cranky, cross, diaphonic, differing,
   disaccordant, disagreeable, disagreeing, disconsonant, discordant,
   discrepant, disharmonic, disproportionate, dissentient, dissident,
   dissonant, divergent, flat, grating, harsh, hostile, immelodious,
   immiscible, inaccordant, incompatible, inharmonic, inharmonious,
   jangling, jarring, musicless, negative, nonmelodious, off, off-key,
   off-tone, out of accord, out of pitch, out of tone, out of tune,
   out of whack, raucous, repugnant, sharp, shrill, sour, strident,
   tuneless, uncongenial, unharmonious, unmelodious, unmusical,
   untunable, untuned, untuneful, variant