It was originally intended to be on their 1979 album The Wall, and appeared in demo versions of The Wall, but was omitted due to the time restraints of the vinyl format. In its place is a much shorter song, titled "Empty Spaces", which segues directly into "Young Lust". This was a last-minute decision; the album's sleeve notes still feature the song in its track listing, and include its lyrics.

The beginning of the song is the same backing track as "Empty Spaces", but in the original key of D minor. It's a slow, dark progression with a repetitive, electronic drum beat and solo guitar, but where "Empty Spaces" ends and segues into "Young Lust", "What Shall We Do Now?" moves into a second, louder section punctuated with guitar power chords. The transition of D - E - F - E is a recurring theme throughout the album, heard on "In the Flesh?", "In the Flesh", "Waiting for the Worms", and the three "Another Brick in the Wall" songs. The long verse is played with D minor and A minor chords. Where the album's main character, Pink's question about how he should fill out the gaps in his wall was of a rhetorical nature in "Empty Spaces", "What Shall We Do Now?" lists the diversions, possessions, and vices of a rock star ("Shall we buy a new guitar / Shall we drive a more powerful car / Shall we work straight through the night / Shall we get into fights / Leave the lights on / Drop bombs ....") in response.

The two tracks are easily confused. The tape speed for "Empty Spaces" was sped up, to raise its key to E minor, with re-recorded vocals and guitar. The members of Pink Floyd have contributed to the confusion regarding the identity of this track, misidentifying "What Shall We Do Now?" as "Empty Spaces" on multiple occasions, such as in the track listing for the film version of The Wall, and on Waters' The Wall Live in Berlin. On other occasions (such as the officially released live version), the first and second parts of the track are divided and identified as "Empty Spaces" and "What Shall We Do Now?" respectively, even though they are in fact two distinct parts of the same song, the first of which was later intended to be reprised as "Empty Spaces". (This is based on the original lyrics and running order as printed on initial vinyl copies of the album.)

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