Like all instruments, the human voice relies on resonance to emphasize a particular fundamental frequency and overtones. For talking, humans use the mouth and larynx to form two resonance cavities which produce vocal formants that shape the buzzing of the vocal folds into distinct sounds. Other phonemes require attack and ending frequencies produced by starting or stopping the air flow with the lips or tongue. Singers train their vocal folds, larynx and mouth to have very clear resonances. They are helped by being gifted with nasal and lung cavities that accentuate pleasant overtones.