Opera singers have to use the extreme limits of their voice range. Many pedagogical and scientific sources suggest that the highest pitches reached in classical singing can only be produced with a so-called “whistle” voice register, in analogy to ultrasonic vocalizations of mice and rats. Opera singers have to use the extreme limits of their voice range. Many pedagogical and scientific sources suggest that the highest pitches reached in classical singing can only be produced with a so-called “whistle” voice register, in analogy to ultrasonic vocalizations of mice and rats. Other Molecular & Computational biology Phys.org – latest science and technology news stories