Instruments used in the song include a LinnDrum machine, Roland SH-101 keyboard for the bass, and a Roland RE-501 loop echo to add warm backing vocals. "The Promise" is in the key of C major.
The instruments featured in "The Promise" include a LinnDrum machine, a Roland SH-101 keyboard generating bass lines, and a Roland RE-501 loop echo adding depth to the backing vocals. The song's overall tone is established within the key of C major.