The simple device of a repeated note in some of its musical guises: as the cry of a hen, the sound of a shivering chorus (borrowed from Lully by Purcell); two stuttering lovers (The Magic Flute), a Handel Fugue subject, a Gabrieli Canzona. a Monteverdi Trillo. a balalaika band, Ligeti's continuum and Liszt's La Campanella. Requests from the under-20s, introduced by CHRISTOPHER HOCWOOD