Once upon a time, John Coxon and Ashley Wales, otherwise known as Spring Heel Jack, were a fairly straightforward drum 'n' bass outfit.

As time moved on, they increasingly pushed the boundaries of the genre (collaborating with Everything But The Girl on their top ten hit Walking Wounded) and, eventually, with top jazz men such as John Surman showing up on their albums, they ceased to be a drum 'n' bass act at all.

In the process, they may have alienated much of their original audience but they have gained a new following.

Currently on tour to promote their new album, Amassed, they filled the Corn Exchange almost to capacity.

Amassed features such leading free-jazz exponents as Matthew Shipp, William Parker, Han Bennink and Evan Parker, as well as (somewhat bizarrely) Spiritualised frontman Jason Pierce.

All too often, such promising collaborations fail to live up to their potential, the jazz musicians simply used to add occasional colour to machine-generated beats.

But this is a sensitive and genuinely-collaborative effort with its feet firmly in avant-garde jazz territory.

This music is not for the faint-hearted and some audience members walked out when a recognisable melody failed to emerge after the first 15 minutes.

But those of us who stayed were in for an excellent performance, somewhere between Ornette Coleman gone electric and Miles Davis circa In A Silent Way.

Of course, there is a fine line between innovation and over-indulgence and there were times when they veered on to the wrong side.

Tearing paper and scrunching plastic bottles next to the microphone seems a little tired and they could have done with less distorted guitar from Coxon (his periods at the piano worked much better).

Certainly Jason Pierce didn't need to spend the entire gig with his back to the audience.

Overall, however, fans of avant-garde jazz couldn't have asked for much more.

As for everyone else, as Wales said: "You can't please everyone all the time, you have to follow your own path. We just get on with making music."

Long may they continue.