According to James M Keller, "Structural experimentation and orchestral sonorities notwithstanding, the most striking aspect of Glass' Symphony No. 2 may be the ways in which melody and harmony interlock in a polytonal fashion.[3] Glass has commented on his use of polytonality in the work: "The great experiments of polytonality carried out in the 1930s and 40s show that there's still a lot of work to be done in that area. Harmonic language and melodic language can coexist closely or at some calculated distance, and their relationship can be worked out in terms of either coexisting harmonies or ambiguous harmonies. ... I'm more interested in the ambiguous qualities that can result from polytonality — how what you hear depends on how you focus your ear, how a listener's perception of tonality can vary in the fashion of an optical illusion. We're not talking about inventing a new language, but rather inventing new perceptions of existing languages."[4]