Motor performance is accompanied by neural activity in various cortical and sub-cortical areas. This intricate network has to be delicately orchestrated. We analyzed the role of beta synchronization in motor learning using magneto-encephalography combined with electromyography. Cortico-spinal synchronization in the beta band was found to be of particular importance in establishing bimanual movement patterns in the context of a 3:2 polyrhythmic (isometric) force production task. Its dynamics correlated highly with the learning of this complex bimanual motor skill. We submit that the cortical dynamics entrains the spinal motor system by which cortico-spinal beta synchrony serves higher-level motor control functions as primary means of information transfer along the neural axis. © 2009 Elsevier Inc. All rights reserved.