Even Mozart, who himself played the viola, wrote only one concerto for it, and in it the instrument has to share the solo spotlight with the violin. Their long relationship as the Jan and Marcia Brady of the orchestra began, legend has it, because violists were mainly recruited from the ranks of superannuated violinists who could no longer be trusted to handle their more prominent, demanding parts. So composers tended to write easy, uninteresting viola parts, which meant that few talented musicians were inspired to learn to play it. This Catch-22 cycle of mediocrity ended only in the 20th century, when composers began to take the darker-, richer-, and sexier-toned instrument more seriously. Now we have a whole weekend devoted to the viola: the Aronoff Festival Concerts. For the 21st year, the Max Aronoff Viola Institute will present solo works and chamber music (by Bolcom, Brahms, Britten, and others) highlighting this neglected middle child—including a piece for 12 violas, Nancy Roth's The Unanswered Call.