Sweet Billy Pilgrim + Portico Quartet, Manchester

There's a famous quote from Louis Armstrong that goes along the lines of 'if you have to ask what jazz is, you'll never know.' And certainly you could have scratched your head last night at this Sweet Billy Pilgrim and Portico Quartet gig and wondered, 'is this jazz?'. And moments later, you probably would have answered, 'does it actually matter?'

First, Sweet Billy Pilgrim. They were the token band no-one had ever heard of on the Mercury shortlist this year, but as usual with these things, completely deserved their nomination for Twice Born Men. It's a lovely record which I reviewed for Metro at the time: a bit folky, a bit proggy, a lot Elbow and, yes a bit jazzy in the switching time signatures.

The acoustics of the RNCM Theatre are incredible, which can sometimes do bands with a more traditional rock set-up a major disservice - every craggy vocal is amplified - but Sweet Billy Pilgrim rose to the occasion: There Will It End in particular sounding almost hymnal in its harmonic grace.

As they spoke of being their own roadies, getting stuck on the motorway on the way to the gig, of how their first record was annoyingly hard to get hold of, you wished that EMI would perhaps back them with a bit more cash - they deserve it. But then, they're not exactly youthful popstars with a huge hit waiting in the wings. Maybe, it's better this way.

Portico Quartet are definitely youthful. Scarily, brilliantly so. Surely it's only the inquisitive nature of youth which would encourage Nick Mulvey to buy a hang (like a mixture between a steel drum and a gamelan) at a festival, and make its uniquely mournful but somehow uplifting sound the centrepiece of his quartet.

Are they a jazz crossover band? They certainly look like they should be in a hip indie band, but anyone who grew up with indie music will have deep seated suspicion of the clattering saxophone solos on some of the tracks. This was definitely jazz. But it was never a show-off jam session: frequently, Portico Quartet sounded absolutely incredible - John Leckie has produced their new album Isla, and there's definitely an element of Radiohead to their sound, a beauty, depth and balls that means they steer well clear of the chin stroking brigade. The drumming is astonishing - you can see why the blogosphere buzz was as much from DJs as jazz fans.

Essentially, if you like Pyramid Song, and can imagine that without vocals, extended to a hypnotic eight minutes of hyperactive instrumental music, you've got Portico Quartet. And maybe, without knowing it, you've 'got' jazz, too.