Coincidentally, putting emphasis on 2nd beat and 4th beat, Charlie Parker, Dizzy Gillespie, Charlie Christian and some others start playing Off Beat. This is the original of Be Bop.

When one thing ripens, in this case Swing Jazz, new trend arises.

On the other hand, big band makes different trend. Stan Kenton, Boyd Raeburn and some others direct another trend called "Progressive". This new music is characterized by new harmony, and later on, it changes its name to Cool Jazz.

Much later, my favorite Chet Baker starts following the same trend. His movement is called West Coast Jazz that becomes another new trend.
At last, this is the year that Thelonious Monk gets people's attention and that Modern Jazz arise