The primary determinants of musica l foml in tonal music were tonality and theme, withcontrast of tonalities being a generally stronger force than contrast of themes. The declinein tonality as an organizing force has often led to a greater reliance on thematic contrast;but in many pieces, themes, in the sense of melodies, pla ya small or nonex istent part. Themost obvious example is electronic music, where texture, register, dynami cs, and especial MIy timbre are usua ll y more important as shaping elements than themes are. Rhythmic ac-ti vity is another organiz in g factor