Figure 1.

Examples illustrating rhythmic structure in music and birdsong. (A) Example sonogram of a thrush nightingale song consisting of five note types (a–e). The song’s rhythmic structure depends on (1) note intensity and duration (as apparent in the sonogram), (2) note syntax (i.e. sequential arrangement of notes of specific intensities and durations), and (3) timing of note onsets, which may either be under control of the bird, or an epiphenomenon of stringing together the vocal gestures required to produce the note sequence. (B) Score of the song “Happy birthday”, with blue shading indicating a recurring rhythmic motif: note timing in the different instances of the motif is the same, while pitch is variable. The third rendition of the motif is slightly modified at the end, containing one additional note instead of ending on a half note, which is here symbolized by the jagged right edge of the blue box. Yellow shading indicates a drift (slowing down of notes, or ritardando in musical terminology).