An important challenge in the study of speech production is to gain theoretical understanding of how laryngeal and supralaryngeal movements are coordinated, and to determine which factors influence this coordination. This study investigates how these movements are coordinated during the production of completely voiceless words and sentences in Tashlhiyt Berber. Results show that the glottis does not simply remain open but that glottal aperture is continuously modulated in a manner that can be related quite systematically to the phonetic nature of the segments present in the sequence.