Pairs of musicians were placed apart in isolated rooms and asked to clap a rhythm together. Each person monitored the other’s sound via headphones and microphone pickup was as close as possible. Time delay from source to listener was manipulated across trials. Trials were recorded and clap onset times were measured with an event detection algorithm. Longer delays produced increasingly severe tempo deceleration and shorter delays (< 11.5 ms) produced a modest, but surprising acceleration. The study’s goal is to characterize effects of delay on rhythmic accuracy and identify the region most conducive to ensemble playing. The results have implication for networked musical performance. Network delay is a function of transmission distance and / or internetworking (routing) delays. The findings suggest that sensitive ensemble performance can be supported over rather long paths (e.g., San Francisco to Denver at about 20 ms, oneway). The finding that moderate amounts of delay are beneficial to tempo stability seems, at first glance, counterintuitive. We discuss the observed effect. 1.