“Mozart’s original score for the 1791 opera The Magic Flute called for a glass harmonica or keyed glockenspiel to represent a set of magic bells. The instruments were obscure even in Mozart’s day but more than 200 years after his death they no longer exist and no one knows how they worked.” Modern orchestras usually use a celesta, but that won’t work for period-instrument bands. Then a London organ maker set to work on solving the conundrum.