Abstract
In this article we made a comparison of the timings of the down and up beats in eighth notes of Charlie Parker, Lester Young, and Coleman Hawkins by using a sound editing software program. A “delayed ratio,” a “bounce ratio,” and an “upbeat ratio” were defined as the duration ratio of the length between the onset of the bass and that of downbeat divided by one beat bass, the duration ratio of the downbeat divided by one beat bass, and the sum of delayed ratio and bounce ratio, respectively. The delayed ratio and the upbeat ratio became larger from Hawkinsʼ era through Youngʼs to Parkerʼs, whereas the bounce ratio became smaller from Hawkinsʼ era to Youngʼs and Parkerʼs. In this way the main change of the timing of eighth notes is considered to have occurred during the transition from swing jazz to bebop from the late 1930s to the mid-1940s. It is also speculated that especially a large delayed ratio by Parker was passed on to Modern Jazz.
