"...We all knew it was going to be massive."
Not my favorite song, by not my favorite band, in not my favorite genre. But there's a lot to hear on this track, and a lot to like. The backing drum part, performed by Roger Palm rather than regular Abba drummer Ola Brunkert was influenced by two sources. The first, and most commonly referenced is George McCrae's Rock Your Baby, a track from 1974. The other is the album Dr. John's Gumbo from 1972. The drummer on that album, Fred Staehle was a regular performer with Dr. John.
The underlying bass guitar works with the drums to keep the dance groove going. That's what you're dancing to; that's what you're always dancing to, drums and bass. Abba adds a lot of other sounds to this track. Synth strings and synth woodwinds as well. There's also real strings on the track. We've also got piano and electric piano. The pianos are doing a lot of work, multi-tracked and playing over the whole song.
Vocally 90% of the work is handled by the two women of Abba: Agnetha and Anni-Frid. Interestingly, they have a completely shared vocal part. They sing the song entirely together instead of trading verses or phrases. Most of it isn't harmony either, they are both singing the same note. It's an unusual technique to be sure, but much like a 12 string guitar, it provides a fuller ringing sound. the song was written by the two men of Abba: Björn and Benny as well as their manager and frequent lyrical collaborator Stig Anderson. The song is a fairly straightforward paean to a young female dancer who is only concerned with the dance and finding a guy, any guy, to share that dance with.