off-key

from WordNet (r) 3.0 (2006)

off-key
    adj 1: inaccurate in pitch; "a false (or sour) note"; "her
           singing was off key" [syn: {false}, {off-key}, {sour}]

from The Collaborative International Dictionary of English v.0.48

off-key \off-key\ adj. & adv.
   Deviating from the proper pitch; -- of a musical note or
   series of notes; as, an off-key note; to sing off-key.

   Syn: false, sour.
        [WordNet 1.5]