It's a typical moment of contemporary musical culture. The month's big idea in musical debate has been to oppose "new new music" and "old new music", the latter meaning modern classical work that speaks to almost nobody. The "old new" is effectively dead, having declined into a cult of composed objects separate from the act of performance. Hence the rise of "new new", or communicating creatively. It's not what you do, it's the way that you do it.
That makes Birtwistle in a London Sinfonietta concert "old new" with a vengeance. So is anything in a London Sinfonietta concert, even if it's by Aphex Twin. But Aphex Twin in a club is "new new", so is Wu Man playing Chinese-American pieces in an all-Asian Prom and young, eclectic jazz musicians playing anywhere.Sirinu working with Rumillajta is an entirely contemporary phenomenon - the materials may be traditional but the music making is new. The night before, when the Familia Valera Miranda from Cuba made their UK debut at the Purcell Room, composers and critics and players from the London Symphony Orchestra were there to hear them among the expected Latin American crowds. It would be stretching a point to call son music new. But think of its relationship with the diverse musical experience of the audience, and an innovative process is certainly going on.
In any case, the Familia Valera Miranda turned out to be full of creative energy. Solo and group singing alternate rapidly against two guitars, three percussionists and a bass. Jazz-like improvisations take wing on steely guitars or sometimes drums.
Once a number gets going, heavy downbeats disappear in a springy, syncopated pulse. Purcell Room regulars have become used to seeing a few people dance, but this time they were on their feet in dozens.
Nothing so pure from Rumillajta: a more passive audience in the bigger Queen Elizabeth Hall was noisily happy to lap up their polished act. If you are into the usual liberal icons of the Andes - panpipes, condors and so on - this is the music for you. Their guest performers were another matter. In 15 years the public has moved on to take less lavishly packaged music in its stride. Sirinu were a pointer. Their mix of speculative Andean sounds and courtly Spanish music had a disconcerting naivety about it. In this context theirs turned out to be the exotic act: a neat reversal of roles. Ears accustomed to Latin music heard intriguing sounds.
Even so, before the second half took off into general partying, the concert's peak moment belonged to another guest, the solo Quechua singer Luzmila Carpio. Her voice flew into octaves untouched by coloratura sopranos to produce a powerful, whistling timbre. What broke through any gawp factor was the expressive force with which she put across her songs. And that brings back the nub of the debate. Never mind whether music is as new as today's paper - if it can't speak, what is the point?