Can Musicians Track Two Different Beats Simultaneously?

The simultaneous presence of different meters is not uncommon in Western art music and the music of various non-Western cultures. However, it is unclear how listeners and performers deal with this situation, and whether it is possible to cognitively establish and maintain different beats simultaneously without integrating them into a single metric framework. The present study is an attempt to address this issue empirically. Two rhythms, distinguished by pitch register and representing different meters (2/4 and 6/8), were presented simultaneously in various phase relationships, and participants (who were classically trained musicians) had to judge whether a probe fell on the beat in one or both rhythms. In a selective attention condition, they had to attend to one rhythm and to ignore the other, whereas in a divided attention condition, they had to attend to both. In Experiment 1, participants performed significantly better in the divided attention condition than predicted if they had been able to attend to only one rhythm at a time. In Experiments 2 and 3, however, which used more complex combinations of rhythms, performance did not differ significantly from chance. These results suggest that in Experiment 1 participants relied on the composite beat pattern (i.e., a nonisochronous sequence corresponding to the serial ordering of the two underlying beats) rather than tracking the two beats independently, while in Experiments 2 and 3, the level of complexity of the composite beat pattern may have prevented participants from tracking both beats simultaneously.