I found out recently that it was written for Jeff Beck. Wondrous.
"Jeff Beck was an admirer of Wonder's music, and Wonder was informed of this prior to the Talking Book album sessions. Though at this point he was virtually playing all of the instruments on his songs by himself, Wonder still preferred to let other guitarists play on his records, and he liked the idea of a collaboration with Beck, a star-in-the-making guitarist. An agreement was quickly made for Beck to become involved in the sessions that became the Talking Book album, in return for Wonder writing him a song."
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