Although now most familiar as the central feature of jazz, improvisation played a significant role in the western classical tradition until well into the nineteenth century, especially during the Baroque period.

The basic similarity between the two is that both use the underlying harmonies of a given musical piece as a basis for an improvised performance. In the age of the Baroque, improvising musicians would be given what is known as a "figured bass" score, which would supply the bass line and the numerals designating the required inversion of the harmonies.

The style which had the most in common with improvisational performance practice of the Baroque era was the New Orleans jazz of the early decades of the twentieth century, which shared its polyphonic texture. While the musicians of the latter style were of mixed levels of musical literacy, all had sufficient mastery of the harmonic and rhythmic conventions of the idiom to improvise the complex, intersecting lines which defined it.

As jazz continued to develop, it gradually moved away from this polyphonic style to place the individual soloist in the foreground with the harmonic accompaniment, usually provided by the piano, taking a less prominent role. The resulting music, essentially homophonic in texture, was quite dissimilar to that of the Baroque period.

Another obvious dissimilarity between the two idioms is the importance of percussion and rhythm to the effect of jazz. Whereas in Baroque music, harmonies and countermelodies may be improvised, the rhythmic accompaniment is usually fixed. In contrast, drummers in the jazz idiom often have considerable flexibility in establishing metrical limits and thus play a powerful role in shaping a given performance.