Eno album Low (1977), whereas Symphony No. 2 is described by Glass as a study in polytonality. He referred to the music of Honegger, Milhaud, and Villa-Lobos as possible models for his symphony. With the Concerto Grosso (1992), Symphony No. 3 (1995), a Concerto for Saxophone Quartet and Orchestra (1995), written for the Rascher Quartet (all commissioned by conductor Dennis Russel Davies), and Echorus (1994/95), a more transparent, refined, and intimate chamber-orchestral style paralleled the excursions of his large-scale symphonic pieces. In the four movements of his Third Symphony, Glass treats a 19-piece string orchestra as an extended chamber ensemble. In the third movement, Glass re-uses the chaconne as a formal device; one commentator characterized Glass's symphony as one of the composer's "most tautly unified works". The third Symphony was closely followed by a fourth, subtitled Heroes (1996), commissioned the American Composers Orchestra. Its six movements are symphonic reworkings of themes by Glass, David Bowie, and Brian Eno (from their album "Heroes", 1977); as in other works by the composer, it is also a hybrid work and exists in two versions: one for the concert hall, and another, shorter one for dance, choreographed by Twyla Tharp. Another commission by Dennis Russell Davies was a second series for piano, the Etudes for Piano (dedicated to Davies as well as the production designer Achim Freyer); the complete first set of ten Etudes has been recorded and performed by Glass himself. Bruce Brubaker and Dennis Russell Davies have each recorded the original set of six. Most of the Etudes are composed in the post-minimalist and increasingly lyrical style of the times: "Within the framework of a concise form, Glass explores possible sonorities ranging from typically Baroque passagework to Romantically tinged moods". Some of the pieces also appeared in different versions such as in the theatre music to Robert Wilson's Persephone (1994, commissioned by the Relache Ensemble) or Echorus (a version of Etude No. 2 for two violins and string orchestra, written for Edna Mitchell and Yehudi Menuhin 1995). Glass's prolific output in the 1990s continued to include operas with an opera triptych (1991–1996), which the composer described as an "homage" to writer and film director Jean Cocteau, based on his prose and cinematic work: Orphée (1950), La Belle et la Bête (1946), and the novel Les Enfants terribles (1929, later made into a film by Cocteau and Jean-Pierre Melville, 1950). In the same