The Danish String Quartet members are rightly hailed both for their sterling technique and their adventurous approach to programming. DSQ will present a very different yet no less intriguing program, juxtaposing two classic works by Schubert—the beloved “Rosamunde” quartet and a quartet arrangement of the lied “Gretchen Am Spinnrade” (“Gretchen at the Spinning Wheel”)—with a new work co-commissioned by Washington Performing Arts from the esteemed contemporary Icelandic composer Anna Thorvaldsdottir.