This is Mozart's Kegelstatt Trio. Mozart wrote it for clarinet, viola and piano, but this recording is augmented by percussion and a chorus: Daphne banging her cooking pots and a choir of company arriving for dinner. It is a preprandial jam that Charlie recorded in the living room after an initial read-through. The violist had performed it professionally years before and the pianist, Robert Horvath, was playing it for the first time. If the piano sounds unusual, that's because it is unusual, a Mathushek grand from 1933.