Introduction. The purpose of this study was two-fold: (1) to study training in rhythmic performance, and (2) to improve and further standardize a measure of rhythmic auditory-motor coordination which can be used as one of a series of tests in the prediction of success and ability in musical performance.1Apparatus. The apparatus used in this experiment was the Seashore phonographic chronograph as adapted by Seashore, R. H.( 22). The latent time of the telephone receiver was found to be negligible, and the latent time of the pen magnet to the crest was .013 sec. In the experiment this was corrected by setting the pattern one-hundredth of a second forward. Two brads placed to correspond with the contact points enabled E to adjust the paper to this desired position. Following the suggestion of Ream (16) and Seashore ( 22), the telegraph key with a resistance of 100 g., with amplitude of 3 mm., was used in this experiment. The key had silver contact points which were cleaned after every third trial.The regularity of the phonograph motor was tested by the use of an adaptation of Seashore's (21) stroboscopic method of reading vibrational frequencies. An electrically driven tuning fork of 50 d.v. was attached to a telephone transmitter which was connected to a neon lamp. A stroboscopic disc containing 50 dots was placed on the phonograph and a record used as a dark background so that the dots would be more perceptible. In order to