Echoes, the curse of the concert hall. are today traced in music by Christopher Hogwood and found to have definite virtues. Vocal examples are found in Elijah by Mendelssohn, Audi Coelum from
Monteverdi's Vespers and The Witches' chorus in Dido and Aeneas by Purcell. Sweelinck and Vivaldi offer instrumental echoes, and Bach actually volunteers a joke. This unexpected repartee is drawn from record requests from the under-20s.