The Sinfonietta, a work in three movements, was sketched around 1960. However due to extensive revisions, the first public performance did not take place until 1969 by the Toronto Symphony, under the direction of former music director Karel Ančerl.

The first of the work's three movements, Allegro, is characterized by themes of great rhythmic vitality, alternating with melodic lines of a lyrical nature.

The next movement is an expressive Adagio, which leads into a moderately fast, march-like Allegro interlude. The last part of the movement returns to the adagio mood of the beginning, this time with muted strings, and the music sounds as if it is coming from a great distance.

The Allegro finale is a brilliant toccata-like showpiece for the strings, wherein the fast, uninterrupted 16th motion never takes a rest.