The Trio in E flat, Op. 38 is a 1805 arrangement of the earlier Septet in E flat, Op. 20 by Ludwig van Beethoven. The original piece, completed in 1800, was scored for clarinet, horn, bassoon, violin, viola, cello and double bass. This version was rewritten for clarinet (or violin), cello, and piano. The overall layout of the work resembles a serenade, closely mimicking Mozart's K. 563 trio, but enjoying substantial additions. Conductor Arturo Toscanini rearranged the string section of the Septet so that it could be played by the full string section of the orchestra, but he did not change the rest of the scoring.