This chapter examines the resonator on its own merits by means of the whispered voice so that this reinforced and amplified to the full by the open, expanded resonator. The length and mass of the cords determine the voice type. Thus, the bass voice will have longer, thicker cords than the baritone, and the tenor's cords may not be as long as those of the baritone. The closing and opening of the vocal cords and the rate at which this occurs is instinctive, and must remain so. In sustaining a vowel, unsteadiness of pitch is frequently heard. This refers to minute variations in frequency throughout the duration of a note which produces the effect known as tremolo. The note should be full and clear with no trace of a woolly or breathy quality. If the slit closes too soon in which case the cords are separated violently before the note begins. This effect is known as a glottal stop.