Final answer:
The true vocal cords, part of the glottis, are the primary structures responsible for producing sound. They are membranous folds that oscillate to create the voice's pitch and tone.
Step-by-step explanation:
The structures most responsible for producing sound are the true vocal cords which are part of the glottis. The true vocal cords are white, membranous folds that are attached by muscle to the thyroid and arytenoid cartilages of the larynx, and their inner edges are free, allowing oscillation to produce sound. The size of these membranous folds differs between individuals, affecting the pitch range of the voice. While the vestibular folds, also known as false vocal cords, support the epiglottis during swallowing, they do not significantly contribute to sound production.