Two for the Price of One is also a special track. Bjorn takes the cheeky vocal about responding to personal ads (‘The cries for help from different people, different ages’), and there’s a hellishly funky chorus with interlocking A&F backing vocals — one of the funkiest lines in their catalogue. The changes are subtly sculpted and dramatic in their contours — hope goes melodically up and disappointment goes down — and just when he reveals the third party in the expected threesome is the mother, there’s a beautiful oompa coda which could only connote the marriage march and its associated bliss. It’s oddly funny, like an mildly bitter in-joke given epic comic treatment (say, of a slightly wry groom to his best man, realising what he's gotten into). It’s on par with McCartney in his medley phase.

The synths are given more prevalence than on previous albums, but the operating principle is always tasteful. In Slipping, there’s a lead guitar solo doubled with synths, and in the second repetition the guitar is mixed out to reveal the synth underneath before returning with guitar — a very pleasing technique. Also on Slipping there’s a harmonic reversal of A&F’s usual range-roles (‘Sleep in our eyes, her and me at the breakfast table…’), that creates a beautifully sympathetic effect of young voices. It could also be dubbed by a single A or F, because I don't think they sing many verses together here. Of course every backing chorus arrangement is perfect and complex. Students of backing harmonies take note.

The Visitors plays at Cold War paranoia and persecution with flanging dissonance and urgent drive (but from a Russian refusenik angle). The (again) doubled synth and guitar solo is strangely triumphant, feel-good running with fist raised. Soldiers transforms what could’ve been a dour song into a bright and jubilant chorus. The rhythm section is so calmly authoritative — pure Abba-unity and confidence of songwriting, fully-fleshed backing vocals and clear melodies. Head Over Heels plays a similar trick with its chorus — follow all the melodies at work in it from its trippity-fragile intro on. The chorus just lurches out of nowhere, like an unexpected key-change. Track the held notes in the vocals. If you looked at the music on paper you’d think it wouldn’t make musical sense. And I love that oblique line about the fashionable snob ‘Pushing through unknown jungles every day’ – the girl who stomps her way through relationships.

I Let the Music Play is a bit of an exception in terms of form. By this stage Benny & Bjorn were moving toward operatic showtunes and minimusicals with stagey themes and big, big choirs. I love listening to them in interviews, I mean they were pretty canny producers and craftsmen, but the casual ease with which they toss off phrases like '... and behind all those vocals you'd then put your *choirs*  ...' (asterisks mine) as though multitrack recording is only fulfilled with massive choirs on every available track. Good old success, throwing money at the formula.

When bands stop touring and concentrate on studio work, especially the big-ass talents, their albums often become more intimate or emotionally revealing. Visitors is probably Abba’s highest expression of emotive studio mastery, and it doesn’t sound like it was tossed-off between tours. With ample time-distance, I now find something sad about top-notch songwriter/bands that have astounding success and dizzying creative peaks (I mean the genuine artists, the ones that really deliver the goods to match their popularity) and their inevitable downward stroke or dissolution. I don't mean when the coke and rehab divorces clear; I mean the indirect humanity that shines thru the cracks with such affecting colour, like on this late album.

In terms of song values and melodic craft, this is the peak of songwriting creativity. It’s almost cloyingly mature, and yet saddening that these amazing melodies are largely devoted to breakups and their typically adult aftermath. Not because these are melodies and choruses I seem to have always known, and hence regard timeless, but because they are genuinely instructive of how good songs are put together and arranged for dramatic effect. This is what’s surprising about The Visitors after all these years – the realisation that it’s all incredibly good stuff, that it will carry on.

All these multivalent sadnesses: the breakups and the vocals they inspire (vocals that cannot help betraying their depth), the tension of beautiful melodies married to dark or soul’s-lonely-night themes, and the demise of band that’s reached its last great peak. Though it wasn’t planned as the final release (and they did more work together), it’s still the most mature album they made.

And it’s still a dangerous album for depressives. It sucks you right in.