The twilight of the tonal system -- Scale formations in post-tonal music -- The vertical the dimension : chords and simultaneities -- The horizontal dimension : melody and voice leading -- Harmonic progression and tonality -- Developments in rhythm -- Form in post-tonal music -- Imports and allusions -- Nonserial atonality -- Classical serialism -- Timbre and texture : acoustic -- Timbre and texture : electronic -- Serialism after 1945 -- The roles of chance and choice in twentieth-century music -- Minimalism and beyond.