How the government killed swing:

In 1944, a new wartime cabaret tax went into effect, imposing a ruinous 30% (later merely a destructive 20%) excise on all receipts at any venue that served food or drink and allowed dancing. ... [I]n the next few years, struggling nightclub owners were trying every which way to avoid having to foist the tax on customers.

The tax-law regulation's ... exception had the biggest impact. Clubs that provided strictly instrumental music to which no one danced were exempt from the cabaret tax. It is no coincidence that in the back half of the 1940s a new and undanceable jazz performed primarily by small instrumental groups—bebop—emerged as the music of the moment.

"The spotlight was on instrumentalists because of the prohibitive entertainment taxes," the great bebop drummer Max Roach was quoted in jazz trumpeter Dizzy Gillespie's memoirs, "To Be or Not to Bop." "You couldn't have a big band because the big band played for dancing."

The federal excise tax inadvertently spurred the bebop revolution: "If somebody got up to dance, there would be 20% more tax on the dollar. If someone got up there and sang a song, it would be 20% more," Roach said. "It was a wonderful period for the development of the instrumentalist."

h/t taxprof