Something about Philip Glass I’ve learned over the years is that by asking very little of his music you can sometimes be surprised by what you get. His endlessly repeating, “minimalist” processes of up-and-down arpeggios and simple harmonies are technically banal and brutal. But stop analysing, try accepting, and it’s possible to find in them a glowing innocence that’s tantamount to spiritual grandeur. And it justifies Akhnaten, his slow-moving, sort of spiritual 1980s opera playing currently at ENO.