Catholics will, one hopes, have spent the Easter Triduum on their knees with open hearts. But those who also managed open ears might have observed the way that festivals of sacred music during Holy Week are almost standard practice nowadays. And few are more impressive than the one that happens in the Chapel Royal at Versailles: a space that day-trippers barely glimpse as they shuffle past en route to the Hall of Mirrors, but a spectacular example of early 18th-century French extravagance that somehow manages to be both intimate and monumental.