Frequency dependence of rhythm in periodic tapping

Cross-correlation between successive stresses and time intervals in periodic tapping was analyzed at 15 different frequencies. Three types of rhythmic pattern of stress and timing in the sequencing of taps were identified in their intrinsic regions of frequency above 2.7 Hz. The tapping sequences were temporally grouped into units of two taps in which relatively stressed taps at the top (type I) or end (type II) of the group were preceded or followed, respectively, by the longer time intervals, while type III was a rhythm with 4 meters. These three types transformed to each other reversibly with shift of the frequencies in a way such as ←(f1)^→ type I←(f2)^→ type II←(f3)^→ type III, where critical frequencies were f1 = 2.7, f2 = 4.0 and f3 = 5.0 Hz. The changes of the rhythmic type with the frequencies are discussed in terms of phase transition in which structures of rhythm are reorganized in order to maintain stable control of sequential tapping in each of the three frequency regions.