The closing concert at Pioneer Works is a 90th birthday celebration for Terry Riley, intended to include The Who’s Pete Townshend, but he had to cancel due to injury. Riley’s son Gyan joining Bang on a Can All-Stars and guests. More than a dozen participants play a new arrangement of A Rainbox in Curved Air and a good hour of In C. The elder Riley (who provided a video introduction from Japan) conjures music that is bright, cheerful, celebratory and communal, making a perfect, looping, loopy finale, with all the spirit and focus that make the All-Stars a unique part of the city’s landscape.