I am not sure if it is possible to talk about bebop without talking about Dizzy Gillespie and Charlie Parker. It is even harder to consider the evolution of jazz without these individuals. Still, in my mind it is the relationship between the two that was the most influential in developing bebop and in effect modern jazz.
While Charlie Parker and Dizzy Gillespie seem to have such wonderful musical chemistry, it is worth noting that the 10-year, on-again-off-again relationship was contentious to say the least. Parker's drug use and unreliability became a major issue for Gillespie. So much so that he simply stopped working with him around the mid 1940's precisely at the point that more recordings of bebop began to occur.
In fact, most of Parker's recording for the Savoy and Dial label are with Miles Davis playing trumpet, and not Gillespie.
So the significance of this album is that it falls at a significant point in both the Parker/Gillespie relationship and the development of Bebop. "Bird & Diz" is the the last of what was actually only a few major studio collaborations between the two. While their collaboration existed mostly throughout the early to mid 1940's as bebop developed - this album was recorded in 1950 when bebop as well as Parker and Gillespie had reached their individual heights.
Because of that, we hear a more polished expression than earlier recordings. While a tune like Bloomdido seems to capture the sound and essence of bebop as well as anything, tunes like My Melancholy Baby with its relaxed tempo seems to nod to some of the aspects of jazz that develops throughout the 1950's. The album rounds out with tunes like Relaxing with Lee, An Oscar for Treadwell, Mohawk, Leap Frog, and depending on which issue you get a ton of outtakes.
What is also significant about this album is the other musicians who made up the album including Theolonius Monk, Buddy Rich, Max Roach, Kenny Dorham, Al Haig to name just a few.
To me the sound of Gillespie and Parker playing together is one of those matches that almost seemed pre-ordained. It is the quintessential sound of bebop. This album does two things for me. 1) It provides that scratched-itch of hearing Parker and Gillespie at their evolutionary heights and 2) It leaves me to wonder what could have been if these two could have played together for much longer!