Michael Webber, who has run the concerts held at English Heritage properties including Kenwood House, in north London, for 12 years, has left 16 months before the end of his contract. He criticised the move away from the standard symphonic concerto repertoire towards shorter pieces and snatches of classics that were less demanding for audiences.
The problem was not confined to English Heritage, who put on concerts from Northumberland to Cornwall, but was widespread, he said. "It is part of a much greater cultural trend which I find difficult to accept."
Mr Webber, 71, said he was sad that the music did not seem to be the priority for many of the audience and that the picnicking, which is a feature of the evenings, had taken over.
He also questioned whether it was necessary to have fireworks at the end of every concert, although he accepted the commercial pressures for doing so. Fireworks add a couple of thousand to attendance figures.
However, English Heritage rejected charges of dumbing down. A spokewoman said jazz and popular music had formed part of the programme for some years. Events this summer will include Cleo Laine and John Dankworth and an evening of Andrew Lloyd-Webber music.
"There's a popular demand. We acknowledge the concerts have to be a commercial success. They bring people into a property where they can enjoy music in beautiful surroundings."Reuse content