Sereanade and Impromptu The Serenade and Impromptu by Leoncavallo have been artfully arranged for Trombone and Piano by Ralph Sauer. They are both originally written for Cello and Piano. These two obscure, yet charming and beautiful Neapolitan songs "without words" together are about 6-minutes in length. With the use of bass clef and "ossia" passages, they are playable by even moderately advanced performers.