On Conducting (Üeber Das Dirigiren) : a Treatise on Style in the Execution of Classical Music

The viola is commonly (with rare exceptions indeed) played by infirm violinists, or by decrepit players of wind instruments who happen to have been acquainted with a stringed instrument once upon a time

. I shall appeal to professional executants, both instrumentalists and vocalists, rather than to conductors; since the executants only can tell whether, or not, they have been led by a competent conductor