You may have missed the signs when entering the two cities but, musically at least, Glasgow is now twinned with Chicago. Having already worked with AACM composer George Lewis, the GIO commissioned him to write this piece, which they recorded in 2012 to mark their 10th anniversary. This is not writing in any rigid sense, however: Lewis provided ‘musical circumstances’ that allowed for the free development of spontaneous music. GIO describes the piece as a watershed moment, opening up new possibilities for large ensemble improvisation. Lewis, who plays trombone on the record, writes in the liner notes about the importance to the piece of consensus, negotiation and local intelligence. Rather wonderfully, the liners also describe the record as aiming for ‘social virtuosity’ – ‘virtuosic listening and virtuosic decision-making and problem-solving’ – but add that it's down to the listener to decide to what extent they have succeeded. Spectacularly, for my money.