Maximal pleasure: Terry Riley live in London

But minimalism can also be exciting and innovative, shifting the spotlight from the cheap thrills of melody to rhythm and timbre, engendering a trance-like atmosphere and pushing what we conceive as music to hitherto-unknown frontiers. It lies at the basis of the kosmische of Can, Neu and Kraftwerk, the trance music of Klaus Schulze and his cultural progeny and the electro-dance-punk joyousness of LCD Soundsystem. So it’s quite an honour to have the chance to see one of the pioneers of the genre, Terry Riley, perform some of his epoch-defining work at the London Barbican.

Tonight offers an evening of two halves. The first comprises just Riley and his son Gyan, a guitarist and composer in his own right, performing some of his more recent work (although “recent” in the context of a half-century career is perhaps somewhat relative.) “Mongolian Winds” probably best encapsulates his latter-day sound; jazzier, less repetitive, with a keen rhythmic sense and a masterful way with improvisation. Even at the age of 81, Riley remains an impressively fluid pianist, and although his offspring rarely steals the spotlight, his virtuoso guitarwork vibes perfectly with the tangents and eccentricities of his father.

The second is devoted entirely to Riley’s masterwork, the ingenious “In C”. Composed in 1964, it’s a piece that technically can be played by any given group of musicians, although tonight we have twenty players, incorporating obscure instrumental selections such as the viola da gamba (a fancy violin) and celeste (a fancy piano) as well a more typical array of strings, woodwinds and vocals. The work comprises 53 musical phrases, which each individual plays in order- but they can choose to play each phrase as many times as they like before moving on to the next one (the only stipulation being that they don’t fall too far behind everyone else). It’s therefore a work that changes with every performance, both as a result of the instruments selected and the spur-of-the-moment choices of each performer.

Tonight’s performance made the most of the dynamic potential of the ensemble, with hypnotic stretches of interlocking rhythms giving way to swells of volume, even if it was, ultimately, quite a conservative rendition of what can be an unpredictable piece. The sound balance wasn’t always perfect - the cello and percussion acquitted themselves stylishly, but the three vocalists spent most of the 70 minutes overwhelmed by the rest of the instrumentation - and the semi-conducted climax worked well, but was always bound to upset Riley purists. But even if it wasn’t the most adventurous rendition of “In C” in its fifty-two year history, it was nonetheless a mesmerising, at times breath-taking one, and it was a sobering epiphany to realise how much excellent contemporary music owes its very existence to forward-thinking masterpieces like this. They might call it “minimalism”, but at its best, the pleasure it brings is truly maximal.