The Collaborative International Dictionary of English v.0.48:

Inharmonious \In`har*mo"ni*ous\, a. [Pref. in- not + harmonious:
   cf. F. inharmonieux.]
   [1913 Webster]
   1. Not harmonious; unmusical; discordant; dissonant.
      [1913 Webster]

            Sounds inharmonious in themselves and harsh.
                                                  --Cowper.
      [1913 Webster]

   2. Conflicting; jarring; not in harmony.
      [1913 Webster]

WordNet (r) 3.0 (2006):

inharmonious
    adj 1: not in harmony [syn: inharmonious, unharmonious]
           [ant: harmonious]
    2: lacking in harmony of parts; "an inharmonious (or
       incongruous) mixture of architectural styles"

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "inharmonious":
   absonant, antagonistic, antipathetic, assorted, at cross-purposes,
   at loggerheads, at odds, at variance, at war, atonal, cacophonic,
   cacophonous, cat-and-dog, clashing, colliding, conflicting,
   contradictory, contrary, contrasted, contrasting, cracked, cranky,
   cross, departing, deviating, deviative, diaphonic, different,
   differentiated, differing, disaccordant, disagreeable, disagreeing,
   disconsonant, discordant, discrepant, discrete, discriminated,
   disharmonic, disharmonious, disjoined, disparate, disproportionate,
   dissentient, dissident, dissimilar, dissonant, distinct,
   distinguished, divergent, diverging, divers, diverse, diversified,
   flat, grating, harsh, heterogeneous, hostile, immelodious,
   immiscible, in disagreement, inaccordant, incompatible,
   incongruous, inconsistent, inconsonant, inharmonic, irreconcilable,
   jangling, jarring, many, motley, multifarious, musicless, negative,
   nonmelodious, off, off-color, off-key, off-tone, out of accord,
   out of pitch, out of tone, out of tune, out of whack, poles apart,
   poles asunder, quarrelsome, raucous, repugnant, separate,
   separated, several, sharp, shrill, sour, strident, tuneless,
   unconformable, uncongenial, unequal, unharmonious, unlike,
   unmelodious, unmusical, untunable, untuned, untuneful, variant,
   varied, variegated, various, varying, widely apart, worlds apart