Neither Wolff nor the SPCO is a household name in Britain, and although their recordings have begun to attract attention here, it is anybody's guess how they will be received when they arrive this week for their first British tour. But we ought to be interested in them on grounds of rarity if nothing else. The St Paul is the only full-time chamber orchestra in the US. The country, which boasts a symphony in every self-respecting town, is oddly short of smaller ensembles. Of the handful with a claim to world repute, only the St Paul has constant membership and it is arguably the best.
Wolff has been in total charge since the beginning of this season, although he has been on contract to the orchestra since 1988. An American-prep edition of Simon Rattle, he is dynamic, glamorous, looks younger than his 40 years and admits that his relationship with the St Paul has taken him 'a little bit off the beaten track of what most conductors consider to be a career path'. Most conductors of his talent would have been aiming for the New York Philharmonic or some other front-line big band; and he certainly knows the workings of that world. He served his apprenticeship as an assistant to Rostropovich with the National Symphony in Washington, and made his debut there in classic fashion: substituting at short notice for an indisposed Antal Dorati in 1979. He has also been music director of the New Jersey Symphony, and is credited with having restored its fortunes from the brink of artistic collapse to national distinction in the mid- Eighties. But then he opted for the modest profile of a chamber orchestra. Why?
'For the same reason a lot of St Paul players leave big orchestras to come here: because it offers a way of making music that's less formal, less hierarchical and maybe more interesting. Conducting big can be like being a cop on traffic duty; but here there are just 34 musicians who all have a real stake in what we do, so it's their performance, not just mine. When we rehearse there's an atmosphere of democracy that I've grown to like. We trade ideas, we encourage dissent. It can be frustrating when the union clock is ticking and you're trying out your seventh bowing possibility, but that's the price you pay. I think it's worth it.'
Wolff's other small-is-beautiful argument is that chamber orchestras have a broader repertory: which sounds unlikely until you consider the extent to which period-performance trends have deprived the big bands of their claim on anything before Romanticism and economic practicalities have marginalised their role in everything after it. Squeezed at both ends, the core symphonic repertory now covers no more than 100 years; whereas the SPCO pointedly covers 400 years, from Cavalli to John Adams.
But that makes the SPCO a generalist operation; and in music, generalism has become suspect. How can you credibly cover 400 years of stylistic turnover with the same players, same instruments, and same conductor?
In the late Eighties, the SPCO had a novel solution. It had a triumvirate of equal-status conductors who each brought a specialist's ear to what the orchestra was doing: Christopher Hogwood for early music, John Adams for modern, and Wolff for what came in between. At least, that was the idea. In practice everyone did everything; and by 1992, when Wolff took over the whole show, the rationale of the triumvirate was less than clear. But it did draw expertise into the melting pot, which survives in that Christopher Hogwood remains the orchestra's principal guest conductor.
You cannot call the SPCO a period band, because it uses modern instruments. But it does observe the halfway measure that Hogwood cutely defines as Hip: Historically Informed Performance. And to hear its players switch from Hip-classical to hard contemporary in the same concert is to appreciate one of the quick-change skills that make the SPCO such an extraordinary ensemble. It really can do both; and so can Wolff. 'Conductors,' he says, 'should have a moral obligation not to specialise before the age of 70.'
With that prospect some way off, he is programming his way towards the millennium with a distinctly Rattle-like survey of music history that will get Minnesota audiences to the year 2000 when the calendar does. The British tour represents time out of the schedule - and an opportunity for nostalgia in that Wolff spent part of his childhood here before going to Harvard for a conventional cum laude musical education. His father was a diplomat at the US Embassy - 'I don't know exactly what he did: nothing sinister' - which meant four years of school in scenic Wimbledon. A happy memory? 'It was a very English school.' This may be Minnesota Nice for No.
SPCO plays Brighton, 0273-674357, Thurs; Barbican, 071-638 8891, Fri; Bristol, 0272- 223686, Sat; Birmingham, 021-212 3333, Sun.