The song originated when Phillips was in the group and would often write with Rutherford on 12-string acoustic guitars. The latter had begun to experiment with unorthodox guitar tunings and had the top three strings tuned into F sharp which provided the jangly sound heard in the opening and the chord that signalled the start of the electric guitar solo. The tuning influenced the title of an acoustic piece, "F#" (pronounced "F sharp") that became the basis of "The Musical Box", which was developed further after Phillips's departure. The opening section of the song features both Rutherford and Banks on twelve-string.