Making the changes" was a bebop term that meant
a. getting to a gig on time.
b. understanding the changing nature of music.
c. being able to solo over a set of chord changes.
d. being able to change horns during a solo.
Making the changes is used in jazz to imply that a soloist is adequately navigating the harmonic form of a tune. In this case that is the same thing as being able to solo over a set of chord changes.
