Music promoter Mean Fiddler has accepted a takeover offer which values the company at around £37.9m ($71.3m).
Mean Fiddler organises the popular Reading Festival
The successful approach has come from US giant Clear Channel Entertainment and Irish firm Gaiety Investments.
Mean Fiddler owns the London Astoria, the Reading Festival and 39% of the Glastonbury Festival.
The deal, which is still subject to approval by Mean Fiddler shareholders, will see the firm's founder Vince Power pocket around £13m for his 35% stake.
He set up the company more than 20 years ago.
Hamsard, Clear Channel and Gaiety's joint investment vehicle - which already owns nearly a quarter of Mean Fiddler shares - said the UK firm was "highly complementary" to its existing business.
"Following the acquisition, the Mean Fiddler group will continue to pursue a strategy of delivering world-class event promotion and event management both through its festivals and music businesses in the UK," said Hamsard.
Gaiety Investments owns music promotion business MCD Productions.