After these operas, Glass began working on a symphonic cycle, commissioned by the conductor Dennis Russell Davies, who told Glass at the time: "I'm not going to let you ... be one of those opera composers who never write a symphony". Glass responded with two 3-movement symphonies (""Low"" and Symphony No. 2 [1994); his first in an ongoing series of symphonies is a combination of the composer's own musical material with themes featured in prominent tracks of the David Bowie/Brian 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.