The registration action may be paralleled to the stringing of a piano. The piano string is attached, at the back, to a little metal peg and, at the front, to the pin. The string is tightened, and the pitch raised, when the pin is turned in a clockwise direction, and vice versa. This tightening action corresponds to the crico-thyroid tension. The firmness of the little peg at the back corresponds to the arytenoid tension. If the peg were to “give” (move), or if the pin block is cracked, the piano cannot hold its tuning. Also, if the bridge is cracked the piano will not hold its pitch – the bridge also constitutes the back attachment of the string. The back and front attachments of the string must be firm and hold, if the piano is to retain its tuning. Both arytenoid and thyroid muscles must be strong if the larynx is to hold its tuning. Furthermore, the strength at both front and back ends must hold and, if either one outpulls the other, the stringing is destroyed and the pitch will waver and become untrue.
Stanley, Douglas. Your voice: Applied science of vocal art. Pitman Publishing Corporation, 1957.