Antonyms of adj on-key

1 sense of on-key

Sense 1
on-key, true -- (in tune; accurate in pitch; "a true note")

INDIRECT (VIA harmonious) -> inharmonious, unharmonious -- (not in harmony)

Similarity of adj on-key

1 sense of on-key

Sense 1
on-key, true -- (in tune; accurate in pitch; "a true note")
       => harmonious (vs. inharmonious) -- (musically pleasing)