The Sonata per la grand viola stems from the early 1830s, during which time Paganini had become interested in the viola.  The composition of this work was a reaction to his dissatisfaction with the sketches of a viola concerto that he had commissioned from Berlioz.  He gave the premiere in London in 1834, using an unusually large viola—hence the title.  Violas, from an acoustic consideration, are really too small for their pitch and its effect on the tension on their strings, so performers try to use the largest one that they can hold and reach the positions on.  Paganini’s work is fairly difficult, so it was not played as much over the years as one might expect.  It now has taken its place in the repertoire for virtuoso violists, and is much appreciated.