Grade: B+ “Cheltenham Symphonies”, they used to call them – a catch-all term for the kind of large-scale, traditionally inclined postwar works that found a natural home at the Cheltenham Music Festival. But it was also a sneer: a dig at the supposedly parochial nature of British music in the 1960s and 1970s. Over in Europe, the avant-garde was doing whizzy things with Marxism and electronics. British music, went the narrative, was suburban, outdated and drab. Now listen to John McCabe’s Third Symphony of 1978. McCabe’s orchestration is as gorgeous as a bird of paradise; it shimmers like the colors on the surface of a bubble. Not that there’s anything fragile about McCabe’s musical engineering.