In 1975, Wonder brought the demo recording of the song to Crystal Sound studio in
Hollywood, California, where he further developed its lyrics and chords. Unlike the demo recording, Wonder decided to play the song in the key of E-flat, which he felt better suited his voice and overall "felt better, spiritually". He also developed the song's
choral introduction, which is performed by Wonder using
overdubbing. Wonder provided the song's vocals and played most of the instruments present on the recording: the
Clavinet,
bass synthesizer, and drums. He also added elements of strings using a
Yamaha GX-1, drawing inspiration from the string sounds found in the music of
Al Green. Musician
Eddie "Bongo" Brown contributed
congas to the track. ==Live performances==