One reason the duo chose Malcolm was his keyboard skills, which Whitehead described as "very subtle; every note he plays is designed to enhance the song. In that sense, he's very 'efficient'." As they had with their first album, the group used the Roland TR-808 drum machine but moved the acoustic piano further back into the mix. Song also features many samples, and excepting some sounds taken from the E-mu Emulator library, these were created by the band, including numerous recorded outside, on one instance traveling to the East Lothian coast to sample castanets in a cave. Rather than create digital reverb, Malcolm used natural reverb in a room at Castlesound, where he and the duo spent time experimenting with different instruments. The duo also used many percussive samples on Song, taken from a range of ethnic instruments left behind in the studio by the Blue Nile percussionist Nigel Thomas. Campbell felt aware that "there are certain traps you can fall into," so the duo used a variety of sounds to build up a sense of rhythm on the album's material, as opposed to "deliberately trying to find something different."
