Though they mostly hail from coastal Fife rather than outer space, the Aliens are not quite of this world. Seemingly channelling Eddie "the Eagle" Edwards, Biggles and - most weirdly - Peter Shilton, frontman Gordon Anderson is tonight clad in skiing goggles, fluorescent flying cap (embossed with luminous green brains on each side), sequinned jacket and goalkeeper gloves. But then what else would you expect from the man sometimes known as the Lone Pigeon? After all, his post-Beta Band solo live outings were characterised by unsettling displays of all-too real mental illness that saw him in and out of hospital for the best part of a decade.

Off medication now, Anderson uses his experiences to his advantage, which is just one reason why the Aliens are such a beguiling proposition. Any band formed from the ashes of the Beta Band were never going to be boring (Anderson has teamed up with BB drummer Robin Jones and DJ/keyboardist John Maclean), but this lot are not only exhilarating, they are musically brilliant. And just as Anderson appears to be wearing several outfits all at once, the Aliens sound like a dozen bands, too. Setting Sun is vintage Dire Straits, Only Waiting starts with a pummelling electronic beat and gothic organ before segueing into a Stonesy rock'n'roll wig-out, topped off with a kooky rap, which Anderson delivers while bending over and over like a nodding donkey. There is some jazzy footwork: Anderson rolls out a superior version of the Peter Crouch dance for the crowd favourite, Robot Man.

But best of all are the slower songs. Anderson straps on a harmonica for Tomorrow, which appears to be an ode to a girl he can't have, and Ionas is a Pink Floydian dreamscape that contemplates the size of the universe. You could make parallels between Anderson and Syd Barrett, both geniuses blighted by psychiatric problems. The difference, of course, is that Anderson has come back - albeit as an Alien.

· At the Green Man festival, Brecon Beacons, on August 18. Details: thegreenmanfestival.co.uk