To the Editor: In discussing the larynx, the subject of "This Is the Voice" (March 7), both the reviewer, Mary Roach, and the author, John Colapinto, miss a major point. They skirt the underlying anatomy and overlook the contribution of the hyoid bone entirely. This horseshoe-shaped structure resides immediately under the jawbone and attaches to muscles that help in swallowing and vocalizing. It is our only bone out of roughly 206 that does not contact any others. The howler monkey represents the epitome of the hyoid's development, where the bone is about the general shape of a round-bottomed cup. The hyoid is instrumental in the howler's ability to project its voice about two miles. Given the relative numbers of howlers and humans, it's good that we are not so well voiced.