Then I wonder why they're hardly ever taken... practically every recent opera I've seen or heard comes over to me as mired in the opera house rather than using it as a springboard for the imagination.
Einstein on the Beach is at least as much Robert Wilson's work as it is Glass's; for example it doesn't use an orchestra (which I don't think Glass has much idea what to do with - his original ensemble of amplified winds and keyboards is so much better-suited to the music, which orchestration causes to sound like a series of accompaniments without a foreground). I might if I'd thought a bit longer have included some Maxwell Davies - I found The Lighthouse extremely effective, though once again in a conventional sort of way. I would also have mentioned some of Robert Ashley's theatre pieces, particularly El Aficionado. I'm completely ignorant of Sallinen's work, I'm afraid.

I think I mean all of the above, and probably more. Perhaps it doesn't always have to be so, and perhaps this comes down largely to money, but my ideal music-theatre would be something that can tour and be set up relatively easily in a wide variety of spaces, using more or less the kind of resources that a smallish theatre company would have. The space one performs in, and its associations, communicate strongly to the audience before they've even sat down. Personally I couldn't ever imagine working in either of the London houses and I don't like even having to enter them, and that goes for most of the (few) others I've been in. That's my problem, it might be said! but I'd be highly uncomfortable trying to say the kind of things I'd want music theatre to say in circumstances like that.

No, so I'm still not really sure what you mean by interactivity in this context!

I have (I realise with a shock) four recordings: Davis, Ancerl, Solti, Bernstein. I'd like to recommend the last of these, which appeared on CD last year after a long absence from the catalogue. Soloists include Rene Kollo, Tatiana Troyanos, Tom Krause. The excellent  chorus is the Harvard Glee Club. Some of the Latin pronunciation is a bit bizarre, though, and the narration sounds more like a fireside chat than a declamation.

Pears was too old when he did it with Solti - I'd love to hear his 1951 effort. I find the recording of the Davis rather unsatisfactory, though there is no quibbling with Davis's grip on the piece.

That indeed sounds like a very interesting way of doing things, certainly as concerns the classical repertoire.

Hm... sorry for putting it in the Coffe Bar, I should have foreseen that it would take a more serious direction!

Do you think it might be worth developing new work along the same lines?    PMD has done a few pieces especially for the Orkney community to perform, for example.