For the first time in any of his works involving amateurs, Britten envisaged a large complement of child performers among his orchestral forces, led by what Graham described as "the professional stiffening" of a piano duet, string quintet (two violins, viola, cello and bass), recorder and a timpanist. The young musicians play a variety of instruments, including a full string ensemble with each section led by a member of the professional string quintet. The violins are further divided into parts of different levels of difficulty, from the simplest (mostly playing open strings) to those able to play in third position. The recorders should be led by an accomplished soloist able to flutter-tongue; bugles, played in the original production by boys from a local school band, are played as the children representing animals march into the ark, and at the climax of the opera. The child percussionists, led by a professional timpanist, play various exotic and invented percussion instruments: the score itself specifies sandpaper ("two pieces of sandpaper attached to blocks of wood and rubbed together"), and "Slung Mugs", the latter used to represent the first drops of rain. Britten originally had the idea of striking teacups with a spoon, but having failed to make this work, he sought Imogen Holst's advice. She recalled that "by great good fortune I had once had to teach Women's Institute percussion groups during a wartime 'social half hour', so I was able to take him into my kitchen and show him how a row of china mugs hanging on a length of string could be hit with a large wooden spoon.