Recently, phase transitions (i.e. abrupt changes between different coordinative modes) have been used as a window into the relation between electro-magnetic activity in the brain and the performance of a perceptual-motor task. The present article reports an experiment similar to a pioneering study in this area, published in Phys. Lett. A 169 (1992) 134-144, which focused on tempo-induced transitions from syncopation to synchronization in a unimanual tapping task. In line with the original study, such transitions were found to be a consistent feature of the data and accompanying analyses of the MEG and EEG patterns revealed both in-phase and anti-phase frequency locking between the events, i.e., taps and acoustic stimuli and the corresponding brain activities. In contrast with the original study, however, no transitions were observed from the basic frequency to twice the basic frequency in the MEG and EEG recordings during synchronization. This discrepancy motivated a discussion of some potential problems in the spectral analysis of event-related encephalographic signals. (C) 2000 Elsevier Science B.V.