Well, up to a point. Admirable though these enterprises are - and they will certainly break down barriers - you might argue that the best place for a musical performance is a space that has been designed for it. Or redesigned: this week I have been checking out some of the more unlikely venues which London has to offer.
My first stop was a converted chapel in Little Venice called the Amadeus Centre: a lovely space with a first-rate acoustic, where dozens of Miss Marpleses had come to hear a husband-and-wife duo. She played well, but he was excruciating: the pounds 10 ticket seemed exorbitant, even though it did include (for those who stayed for the second half) a sandwich and a glass of wine. On, then, to the lobby of Lauderdale House in Highgate, where another husband-and-wife duo - known as GuitarVokal - did extraordinary things with folk songs from Japan and Sephardic Spain. Everything in their programme was in some way novel; if the performance was rough at the edges, it still had its 25-strong audience on the edge of their seats.
Musical life in London is like an iceberg, whose visible bit - the South Bank-Barbican-Wigmore nexus - is dwarfed by the multifarious, critically- unsung activities below. And if many of these take place in church, that's as it should be, for the concert-hall was an 18th-century invention. For the price of a pound or two in the collection box, you can be royally entertained.
As I discovered in St Martin-in-the-Fields where, for a packed audience, the pianist Magill played some superb Bach and Mozart. "Your seat was paid for by the person sitting in it last week, so please give generously," said the priest in his introductory speech. Like everyone else who does lunch times here, Magill was playing for free, yet there is a long queue waiting to follow him into the hot seat. And if you look at the British Music Yearbook you will see why: nearly 600 pianists are listed. Of these, relatively few will make a reasonable living from concerts. Since the others must still play, they play for free, and to hell with the acoustics (poor in St Martin's, dreadful in nearby St James's Piccadilly).
At the church of St Anne and St Agnes, in a quiet corner of the City, you enter another world. Built by Wren, but now London's main Lutheran outpost, this is a haven where office-workers of the more civilised sort come to consume their sandwiches to music. And you sense an active faith: Wednesday concerts are framed by prayers, and this week's petition, open for signatures, calls for civil rights in Pakistan, while the collection is for disaster victims in Papua. The concert I caught on Monday, by the Isis Trio, was good by any standards: a work by Brahms, and a coruscating new piece by their leader, Timothy Murray. "A trial run" was how they modestly described this, but at the Wigmore it would have been proudly dubbed a "premiere". It's no surprise that these concert slots should be booked up till next spring, or that past performers include many now- famous names. The players, often top professionals taking time off to try out new repertoire, earn pounds 10 each. This really is the bedrock of London's musical life.
THE NEW-VENUE craze may be gimmick-led, but concerts in art galleries have a noble pedigree: that was how Dame Myra Hess helped boost morale in the Blitz. And the tradition continues, in Dulwich Picture Gallery for instance, and at Kettle's Yard in Cambridge. Next month, the Wallace Collection picks up the torch it lit last year, with six Sunday-morning recitals by chamber players who have not hitherto performed in London. "Most concerts are too long," says their organiser, Hannah Horovitz. "At the end of a working day people are tired and jaded. By holding our recitals in a roomful of paintings, we have engaged with an entirely new audience." For music, art, a glass of champers and a croissant, pounds 12.50 doesn't seem a lot.
TELEPHONING ME from the sunny side of Fame Street comes a creaky little New Yoik voice: the Japanese ex-prodigy violinist Midori, with a record to sell and a concert to promote (Festival Hall, 14 October) and, at 27, with enough good works already in the bag to guarantee her a place in heaven. Midori and Friends is a charity devoted to bringing music to children in deprived areas; Midori also gives masterclasses round the world.
But it becomes immediately apparent that she doesn't want to sell me anything. She won't be drawn on the prodigy circus, on the malign part played in it by the media, or on whether she ever suffered stresses and strains.
What advice would she give the next Midori? "Do it because you love it." What she says about her educational work is firmly in the platitude category. I am disappointed.
But I have no right to be. This girl is paid to play, not to manufacture quotes. And her record is wonderful: concertos by Tchaikovsky and Shostakovich under Abbado's baton (Sony), in which emotional maturity is allied to impeccable musicianship. No reticence there.