Phase synchronization within and between the brains during the period of guitar playing. (A) Topological distributions of PLI in a representative pair of guitarists, A and B, at the low theta frequency (3.3 Hz) 800 ms after play beginning of guitarist A. Fronto-central maxima of PLI are shown. (B) Guitar traces and time-frequency diagrams of average PLI for guitarists A and B. PLI was averaged across six fronto-central electrodes. Only significant PLI values (p < 0.01) are shown. Time zero is time locked to play onset of the leading guitarist A. The leading guitarist's finger gesture to start playing together is indicated with a red arrow. The yellow arrows refer to individual guitar strokes. The time course of PLI values at the low theta frequency (3.3 Hz) is depicted below the time-frequency diagram. (C) Interbrain synchronization between the two guitarists measured by IPC at the low theta frequency (3.3 Hz) 800 ms after play onset. Colored lines indicate synchrony between electrode pairs of the two guitarists. Only IPC values higher than 0.51 are highlighted. (D) Time-frequency diagram of the average IPC averaged across six electrode pairs (for further explanation, see Figure 1D and 2B). The time course of IPC values at the low theta frequency (3.3 Hz) is depicted below the time-frequency diagram. High phase synchronization within (PLI in 2B) and between (IPC in 2D) the brains took place not only at play onset but also at the time point of the gesture serving as starting signal, and at the individual guitar strokes. SL = significance level.