ABBA

In April 1975, ABBA were worried that the heady days were over. Waterloo, their song about one girl's surrender in the battle of love, had won the Eurovision Contest 12 long months earlier. Reviews of the group had been positive - even Rolling Stone had said they were putting "new life into... cartoon pop" - but recent UK singles had flopped, and tours were not selling out.

Time then, for a difficult third album featuring reggae, prog, rock and funk, and somewhere in the middle, a giddy SOS. "Here I go again," the first track begins. How could we resist them?

At first, it's odd to think that this was the album that broke Sweden's biggest band; it dashes from genre to genre, with a few massive hits in the middle.

Mamma Mia is now so familiar it's like a nursery rhyme. That chirpy marimba and that chorus - the hooks keeping coming and coming - are now a vital part of pop's DNA.

In it, we find one of ABBA's trademark sad, layered stories, bubbly and joyous to the ear, but full of darker details about "slammed doors", and an "angry and sad" woman that's "not that strong". Lyrical depth and shiny surfaces: here are ABBA, early on, refining their magical formula.

This gets repeated elsewhere, with mixed results. Hey, Hey Helen begins with crunchy guitars before shocking with the tale of a woman that's left her husband and children.

Bang-A-Boomerang and I Do, I Do, I Do, I Do, I Do stick to bouncier pop, the former brimming with advice about compromise within marriage, the latter using the wedding declaration to mask lyrics teeming with insecurity.

Then they play with sound. Tropical Loveland's pop-reggae crossover shows forward thinking but little in way of fabulousness; Intermezzo No 1's Yes-style synth-opus is ridiculous, but occasionally rewarding. Rock Me's late entry into the glam canon suits the band better, Bjorn's screechin'-and-a-squealin' providing particular pleasures.

ABBA doubters will be pleasantly surprised to find the band's desire to experiment here. If that's you, breathe deep and plunge into their back catalogue - there's plenty more depth to explore.

Long-term fans will enjoy the accompanying DVD, and be reminded of an interesting juncture in the quartet's career. As they tilted between failure and success, they threw everything into the mix. Before long, they would have the whole world in front of them.