In On the Road, the music we focus on is jazz, more specifically the American bebop of the 1940’s. Music has religious associations, as Dean sees several musicians as God. It brings about a madness, if associated with drugs. Music also features prominently in the definition of "Beat," as in the beat of a music. This is important in Dean’s characterization of those who "know time." Music becomes here another lens through which to examine America; the jazz is the same, from one city to the next, and is intensely American in its sound and culture.
Just as Sal "shambles after" Dean, unable to partake in the madness, so Dean shambles after music, unable to play himself. This suggests that musicians are the mad heroes to Dean just as Dean is a mad hero to Sal.
Kerouac uses many devices to paint an accurate picture of America at the time of On the Road. The use of music, in particular the accuracy of historical and pop cultural references, underscore the importance of the novel in cultural history.