The experience kept children of eight upwards - and there were quite a few in the audience - thoroughly absorbed. Or, at least, they laughed at the same things I did. The opera harks back to Charles Perrault's earliest version of the tale, in his 17th-century Mother Goose collection, in which nobody comes to the rescue. When the wolf seizes the grandmother, there is just enough suggestion of rape before she wraps herself in a sheet and makes a ghostly retreat. Then Riding Hood, explicitly invited into bed by the disguised wolf, suffers the same fate. A moral in verse follows, lightly but chillingly updated here to rhyme "Leicester" with "molester".
Aperghis has set it for six musicians, who also tell the story and act it out. The members of the Continuum Ensemble wear concert dress and are unable to do without music stands - it's quite intricate stuff - out of which Arden has made a virtue, having them and the pianos moved gracefully around the stage to reinforce the mounting unease of the events.
Compounding it further, the narrative proceeds in repeating and overlapping phrases, so that it takes two steps forward and one back. That's until the final stages, when it switches into fast-forward to reinforce the shock of Riding Hood's unfamiliar demise.
Apart from the pianos, there are three high woodwind and a violin, a deliberately limited sound-palette that has a cumulatively claustrophobic effect. From time to time, one player activates a tuba through several metres of plastic tubing to make scary sounds, to which the audience reacts with hollow mirth.
The show's distinction is in its staging and vocal delivery. It takes quite something to turn a bunch of modern-music specialists into confident actors. But Arden has the musical experience and nous to bring off the adventure.
There was a great atmosphere in the Almeida, too: let the kids in, and the usual new-music endurance test is transformed into a proper evening out.