“It is most unfortunate that, in the teaching of the technic of both singing and playing the piano, and, as far as we know of all the other technics, there has been so much talk about ‘relaxation.’ Absolute relaxation is impossible. Too high a degree of relaxation is undesirable, and the muscles which should be used must come into absolute tension. The muscles which should not be used, and which interfere with the act, should indeed be relatively relaxed. The problem, however, lies rather in the strengthening of the muscles which should be used, and, in practice, the over-relaxed pupil is apt to present the harder problem. This is especially true in view of the fact that the placid, unmusical, undramatic individual is apt to be over-relaxed. The artistic, ‘talented’ pupil is apt to be rather tense and neurotic. Generally speaking it is easier to reduce than to increase the general state of muscle tone.”
Stanley, Douglas. “The science of voice.” Journal of the Franklin Institute 211.4 (1931): 405-455.