If I’m correct, Jazz before the Bop era was primarily Big Band, Vocal Jazz And Standards. Bop really seemed to have launched the more original and creative pursuit of jazz and broke the scene apart from giant bands led by Duke Ellington, Dizzy, Harry James, Count Basie, Tommy Dorsey, etc etc down into small trios, quartets, and quintets helmed by masters of their instruments. Bop was a renaissance in the jazz format, think of it as the jump from The Beatles type of rock to Led Zeppelin/The Doors type of Rock. The music got sexier, more intense, rebellious, violent even lol. That being said pre-bop Jazz is still incredible and remarkably beautiful, it’s just much more buttoned up and predictable. When venturing back through that I recommend starting with albums like Masterpieces by Duke Ellington, Ella & Louis, Benny Goodman at Carnegie Hall and artists like The Ink Spots, Billie Holiday, Nat King Cole, Frank Sinatra etc etc. Its a much sunnier era of music, at least that’s how my mind perceives it! I have a great playlist that dives into that era of music on Spotify if you want me to send it to you. It’s one of my favorites to listen to on any given day.