One of the five most acclaimed New Music chamber ensembles in the world, Kronos Quartet has recorded music from every period, from Machaut to Wagner to Hendrix to Dun. Their Night Prayers collection--which features mainly Eastern European composers--peaks with Sofia Gubaidulina's bristling Quartet No. 4. Expert at traditional instrumentation and composition, Gubaidulina scripts the piece's early parts with vaguely balalaika-like tones that morph into mid- range, stretched notes. The quartet's underlying structure becomes a skittering display of plucked, repetitive notes against which the strings variously slash, sweep, and chatter. Gubaidulina's summation of late-century chamber work is more than striking.