Steve Reich's minimalism has always had an unrelenting rhythmic urgency, but the themes of WTC 9/11 endow his driving ostinatos with a bleak, terrifying power. First, as the Kronos Quartet is accompanied by recorded emergency response calls, Reich uses a simple device to chill the blood: a mechanical busy signal. The following two movements also employ spoken interviews and recordings of Muslim calls to prayer. These are complex choices that make the piece an emotionally raw, unflinching statement. Readings of 2009's Mallet Quartet by So Percussion and 2002's Dance Patterns follow.