If sex is the opera of the poor then most North Londoners know all about Glyndebourne. Going for a summer weekend romp on Hampstead Heath you are likely to be interrupted at strategic moments by a tenor in full cry and pursued by a horde of picnickers. Those of us who were brought up on the Kenwood Lakeside Concerts also tend to remember idyllic evenings sprawled across the slopes, while somewhere in the background a vaguely rehearsed and balanced sound approximating to an orchestra buzzed away with one of the pop classics, punctuated by the regular descent of jumbo jets towards Heathrow.

Anybody who hasn't been for 20 years would have trouble in recognising them now. True, the sensuous charms of timing and setting are still there (and so are the traffic jams at the end). But the musical act is smartened up. There's a wider range of performers, from jazz to the Royal Opera, more or less discreetly amplified. Best of all, both here and at the Marble Hill House concerts by the river in Twickenham, it isn't always Tchaikovsky Five or the New World Symphony .

When did you last hear Arthur Bliss's Piano Concerto, anywhere? Marble Hill this Sunday has it, alongside the fireworks. On Saturday 13th at Kenwood, Howard Blake (above) conducts his own Violin Concerto as well as Delius, Mendelssohn and Beethoven. To be sure of getting in you can book seats in advance, though it's more fun to bring rugs and take a chance on finding that perfect spot on the grass. Locals know a still cheaper alternative that avoids the crowds, though naturally they don't talk about it. Let's just say that musicians have to rehearse, and if you happen to be walking your dog during the afternoon. . .

Kenwood, 7.30pm Saturdays. Marble Hill, 7.30pm Sundays (except 7pm on the 21st) to end Aug, tel: 071-413 1443

(Photograph omitted)