The effects of tempo and role (fast vs. slow hand) on the reciprocal i
nteraction (strength of coupling) between two hands tapping a 2:3 poly
rhythm were examined from the perspective of nonlinear oscillator theo
ry. A measure of the degree of harmonicity was developed, based on the
relative contribution of the tapping frequency to the power spectrum
of the limit cycle phase angle of each individual hand. On the assumpt
ion of fixed coefficients of the dissipative terms in the component os
cillators, comparison of unimanual and bimanual performance with respe
ct to this measure allowed for examination of the effects of the exper
imental conditions on the strength of the coupling. Five right-handed
skilled drummers performed the 2:3 polyrhythm at several tempos and wi
th both hand arrangements (i.e., either the preferred or the non-prefe
rred hand tapped the faster cadence). The analysis revealed an inverse
relation between tempo and coupling strength, and a larger influence
of the fast hand on the slow hand than vice versa. No differences were
observed between the two hand arrangements. The theoretical implicati
ons of these results were discussed in relation to similar and dissimi
lar findings in the literature.