IPA: /ˌɔfˈki/
KK: /ɔfˈki/
In a way that is not in tune or harmony, often referring to music or singing that sounds wrong or unpleasant.
The singer performed offkey, making the audience cringe.
Offkey → It is formed from "off" (from Old English "of", meaning away from or not) and "key" (from Old English "cāg", meaning a musical key or tone). The word "offkey" describes a sound that is not in the correct musical key or tone, hence out of tune.
Think of being 'away from' the correct musical 'key' — that's why offkey means not in tune.
No commonly confused words.