Hallman is composer-in-residence at the Rosenbach Museum & Library of Philadelphia and the Pikes Falls Chamber Music Festival. He has collaborated with leading performers and ensembles. Cellist Alisa Weilerstein performed his concerto for cello and chamber ensemble with the St. Petersburg Chamber Philharmonic in Russia. A series of concerti grossi, inspired by Johann Sebastian Bach's Brandenburg Concertos, was performed by members of the Philadelphia Orchestra, New York Philharmonic, Pittsburgh Symphony, and Cleveland Orchestra. The Cavani Quartet has premiered his compositions. His ballet Alice was performed in April 2010 by the Colette Harding Dance Company in San Diego. He has worked closely with poet Jessica Hornik, and his settings of three of her poems is included in the album "Sprung Rhythm" by the Washington DC ensemble Inscape, which was nominated for the 2014 Grammy award.Grammy.com
