Mahler’s music offers the opportunity for an enrichment of the unilateral identity paradigm in musicological research through the concept of cultural and aesthetic hybridity. This chapter addresses the plurality of idioms, styles, and voices in Gustav Mahler’s music in the context of the cultural and linguistic heterogeneity which characterises Vienna at the turn of the century. Analytical categories are proposed that are able to serve the plurality and hybridity in Mahler’s music; relevant passages in his work are discussed according to these categories: 1. tragic breakdown (of the musical subject); 2. grotesque destabilisation; 3. alienated sound; 4. plurality of voices; 5. metamorphosis and mimesis; 6. thematic instability; 7. hybridity of genres and forms; 8. eclipses of the author