Once upon a time, a beautiful, teenage Glaswegian couple formed a band and recorded a single, perfect album. Then they split, and so did the group, and their tiny label disappeared, too. They may have ended up nothing but a footnote, if Kurt Cobain hadn't personally pestered Sub Pop into distributing their collected works for generations of lo-fi pop outfits from Scotland to Los Angeles to worship.

That is the magical Vaselines legend, breathlessly repeated by fans around the globe, and the legacy that their first new album in over two decades places in jeopardy. It is the reason, despite the well-deserved rave reviews that have followed them from country to country in the two years they've been playing reunion gigs, that Sex with an X needed to strike such delicate balance. No one wants to hear Frances McKee and Eugene Kelly evolve into “mature" instrumentalists -- or cling to the childhood imagery and giggling sexual innuendos the band was known for, as if they had been frozen in time since 1990. Aging gracefully has always been a problem for rock 'n rollers, but when you traffic in twee, it's a veritable minefield.

Thankfully, the Vaselines are more than just grandma sweaters and amplifier fuzz. McKee and Kelly's charmingly silly sense of humour has always provided their best moments, from the rebellious high-school messiah whose mom nags him about his hair in 'Teenage Superstars' to their cover of Divine's wonderfully ironic 'You Think You're a Man', complete with comically orgasmic ooh's and aah's.

That flair for comedy is what elevates Sex With An X, the first single from which bears the blunt title 'I Hate The '80s' and contains the sing-along chorus -- sure to be quoted in every review of the record - "What do you know?/ You weren't there/ It wasn't all Duran Duran Duran/ You want the truth?/ Well this is it/I hate the 80s 'cause the 80s were shit." With that lyric, an unabashedly middle-aged McKee and Kelly are directly addressing contemporary vogues for stupid day-glo leggings and cassette tape fetishes. 'Overweight But Over You' may be the year's bounciest dose of self-deprecation, featuring the killer pick-up line, “Hey, fat mama/I'm a fat man." These songwriters are no longer fresh-faced youths, and these songs wryly acknowledge that fact without descending into mopey mortality trips.

Other tracks are more closely analogous to early Vaselines tunes: 'The Devil's Inside Me', with its comparatively slow pace and afterlife angst, is this year's 'Jesus Wants Me For A Sunbeam'. A rare low point, 'My God's Bigger Than Your God' is a raucous but hackneyed shot of irreverence, like a watered-down 'Sex Sux (Amen)'. And 'Mouth to Mouth' has all the wispy sex appeal of 'Molly's Lips' and 'Slushy'. The addition of guitarist Stevie Jackson and bassist Bobby Kildea, both of Belle & Sebastian, along with 1990s drummer Michael McGaughrin, may have the Vaselines sounding cleaner and fuller than ever before, but they still know how to wield a noisy guitar ('Ruined') and never sound over-produced. That familiar interplay between Kelly and McKee's voices, his rough and hers high and airy, remains sublime.

Sex With An X feels like the best kind of comeback: the organic reunion of two songwriters who've rediscovered how much they enjoy making music together. The Vaselines may well vanish into obscurity for another 20 years - or forever, as their closing track, “Exit The Vaselines," teases. In that case, it's a good thing they've given us one more album that's sure to stand the test of time.