Cool, Jazz and Rock in 1948

I can't access the OED at the moment, so I don't know to what extent this is covered there, but via newspaperarchive.com I found an interesting article relating to the use of "cool" in the jazz world, in the Bridgeport (Conn.) Telegram, July 13, 1948:

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"Hot jazz is dead. Long live COOL jazz!"
That is the startling statement attributed to Leonard Feather, self-styled jazz expert, in a publicity release ...

"Hot jazz, as such, may be on the way out," says Feather, "but it is gradually being replaced by something that can just as well be described as "cool jazz." This phrase is simply a way of describing the younger musicians' new approach to jazz improvisation.
"The old-school jazz created a tension, where the new jazz tries to convey a feeling of rhythmic relaxation. Jazz today tends to be played a fraction behind the beat, rather than right on the beat or even ahead of it."
The term "cool", he points out, is used by many musicians as a synonym for everything good. As examples of "cool" musicians, he cites pianists Dodo Marmarosa, Errol Garner; tenor saxmen Lester Young, Lucky Thompson, Wardell Gray, Allen Eager and Dexter Gordon; alto saxist Charlie Parker, trombonist J. J. Johnson and guitarist Barney Kessel.

In other words, Mr. Feather feels that nothing but the "bebop" type of jazz is worth bothering about.
That we disagree wholeheartedly with Mr. Feather need hardly be pointed out to anyone who listens to our "Rock 'n' Rhythm" program over WNAB these Tuesdays at 7 p.m.
On "Rock 'n' Rhythm" tonight, we are planning a battle-of-music between the "hot" and "cool" types of jazz.

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This is interesting for a few reasons. First, Feather's understanding of "cool jazz" seems related to, but not entirely the same as, the idea of "cool jazz" that began to emerge a year or three later. Feather's "cool jazz" seems to be somewhat bogusly defined, but it's hard to see how it's different from bebop (one wonders whether he was searching for a term to replace 'bebop' or 'bop').
Second, note the name of the Bridgeport show, "Rock 'n' Rhythm". This shows that "rock" was being used in a jazz/blues sort of context and presumably refers to the conservative danceableness of the music played on the show (I'm basing this in part on the hostility the writer shows for Feather's point of view). I've noted before that the very term "rock and roll" can be traced back to the late '30s or early '40s and the idea that this was originally a sexual term that came to be applied to music seems to be a total self-serving myth created by the champions of certain post-Suez musical styles.
Early rhythm 'n' blues, as a style of music distinct from swing or jazz generally, seems to date from this period, and of course that black musical genre was the direct ancestor of the white "rock 'n' roll" genre that emerged after the Suez Crisis (with some hillbilly influence thrown in). I can see how rhythm 'n' blues would have been seen as "hot" in a different way from how the revived Dixieland was "hot". Cf. the "hard bop" style of jazz that developed in the mid-1950s sort of in aesthetic opposition to the cool jazz and West Coast jazz of the early '50s.

Third, Feather reports that musicians were, by this time, using "cool" to mean "good", though I guess we already knew that.