|Written by||Stevie Wonder|
|Source||Songs in the Key of Life (album)|
It was also released as a single, with "Muskrat Love" as the B side. Bernie Hoffer (later to compose the music for Rankin/Bass' Thundercats) arranged both songs. Suzanne Ciani, known for her work on synthesizers, provided "electronic musical effects on the Buchia synthesizer" on "Sir Duke."