In a bid to expand the available repertoire for piano, violin, and cello, the Merz Trio has sought out (and in some cases, created themselves) arrangements for their instrumentation. As a result, their Feb. 11-12 program for the Dallas Chamber Music Society includes a wide range of composers, including Hildegard of Bingen, Thelonious Monk, and Henry Purcell. Some more expected music by Brahms and Schumann will be offered as well.