If you really have to retire from music, as 37-year-old Rossini felt he did in 1830, there are worse ways to go than with the final chorus of William Tell. The foul oppressor has been killed and Switzerland is on the brink of freedom. But far from the expected tarantara, the music dissolves in relaxed radiance, harps melt the world’s edges, and a battered people sinks back into nature amid music of spine-tingling calm that embraces everything from Haydn’s Creation (1798) to the final scene of Wagner’s Rhinegold (1869) with its rainbow bridge to Valhalla coalescing out of thin air, a scene heavily influenced by Tell. Thus did Rossini – rather more than the frivolous note-juggler of popular myth – bestride the nineteenth century.This show has been overshadowed