Vocal coaches Gillyanne Kayes and Jeremy Fisher, authors of This is a Voice, give Michael Rosen a workout. They get him to read against natural pitch and intonation, which proves nearly impossible, and make him match his speaking pace to a walk around the studio. What we do with our consonants and our ability with a tongue twister also turn out to play a part in the ways in which we speak. Producer Beth O'Dea.