Here is the link to the beautiful song Four o'clock drag by Lester Young and Kansas city six:
It this song an example of Bebop?
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No. These recordings were made in 1938, before World War II, and represent a rather simple and highly-melodic blues style which can be used for dancing. Lester Young was indeed involved in bebop in later years, but your example is from before this time period.
Bebop is a form of jazz that did not develop until after World War II. Bebop is characterized by not being danceable, and demanding the full attention and concentration of the listener. Bebop is fast, dense, and more intellectually rigorous, among other things. When bebop first began to appear in jazz clubs, they literally posted signs asking audience members not to try to dance.
The Wikipedia article on Bebop explains it pretty well:
Bebop musicians explored advanced harmonies, complex syncopation, altered chords, chord substitutions, asymmetrical phrasing, intricate melodies and using rhythm sections in a way that expanded on their role.
A classic Bebop piece is characterized by taking the basic chord progression of a well-known Broadway show tune or jazz standard, discarding the melody altogether, making the chord progression dramatically more complicated by complex chord substitution, playing the song at a very fast tempo, and having the soloists compose entirely new melodies in a very complex, chromatic or even atonal manner.
If you want to hear saxophone in the bebop style, listen to the recordings of Charlie Parker after about 1945.
Lester Young's contribution to the early, developing style of bebop can be heard in his recordings with Coleman Hawkins as part of the much larger Jazz at the Philharmonic (JATP) series, on Verve Records.
Here are some of those recordings on YouTube.