We can make many different sounds with our voices, communicating not only with what is said, but also in which context it is said, and who is saying it. This large variability makes the voice a rich channel for communication, but it also presents us with challenges when we try to assess the status of a voice using quantitative measurements, rather than by listening. When voices run into trouble, even more variability can be expected. Voice production is usually described as three processes in sequence: respiration /€“ breathing; phonation /€“ the vibration of the vocal folds; and articulation /“ changing the shape of the vocal tract, which modifies the sound into vowels and consonants. For brevity, let’s look only at some aspects of phonation that can be expected to be clinically relevant.