Avian alien languages are frequently bi-tonal, requiring two sets of vocal cords to pronounce vowels. Humans can use a clip-on keyboard device to speak them. : r/worldbuilding
Vocal Cords (Vocal Folds) & Vestibular Folds of the Larynx | GetBodySmart
Hoarseness: When to observe and when to refer | Cleveland Clinic Journal of Medicine
Vocal cords or vocal folds?
Hoarseness: When to observe and when to refer | Cleveland Clinic Journal of Medicine
Fresh Voices: Researchers Grow New Vocal Cords From Cells
Vocal Folds Stroboscopic Image Processing for Otolaryngology | IntechOpen
Kuno Ref by Wolftacular -- Fur Affinity [dot] net
How do the vocal cords of people with wide singing ranges work? - Quora