Note: Hank Trubey recommends journal articles in the fields of otolaryngology, voice production, and the physiological basis of language. Redundancy in communication. Birdwhistell notes that one out of 3,000 signals are used for communication, the others take a supporting role. Role of emotion in producing nasal congestion of the sinuses that results in changes of resonance. Discussion of tremolo versus vibrato (regular, systematic tremolo) and their use as expressive devices. Vibrato is an attempt to maintain pitch regularity, always seven beats per second, whether a bass or soprano. Trained singers can do things that untrained singers cannot, modifying volume of breath, etc., maintaining even pressure from diaphragm so they don't run out of breath. Damping: voices that leave out partials in a harmonic series acquire a kind of ringing sound. Voices that employ full series sound harsh. Trubey describes his own research in consonant blend production.