Live Nation Entertainment is close to finalizing a deal to acquire about a 50% stake in Insomniac Events for $50 million, according to people familiar with the matter.

Insomniac Events, which produces electronic-dance-music festivals and is known for its Electric Daisy Carnival, which drew more than 300,000 fans to Las Vegas last year, would be a coup for Live Nation, the nation's biggest concert promoter.

Live...