One distinctive feature of orchestral brass instruments is that there is a marked change in timbre with dynamic level. It is generally accepted that the explanation for this behaviour is shock-wave generation within the body of the instrument. However, it has also been suggested that changes in the nature of the players' lip vibration with increasing amplitude could play at least a small role in generating this distinctive 'brassy' sound. Previous studies have shown that the brassy sound cannot be accounted for by a dramatic change in the behaviour of the Up opening area during extremely loud playing. The experiments described here are designed to test the hypothesis that variations in the motion of the lip parallel to the airflow into the instrument may help produce the 'brassy' effect. A high speed digital camera and transparent mouthpiece are used to capture the motion of the lips in the plane perpendicular to the face of the player for different dynamic levels. Measurements have been taken over a variety of instruments and musicians and over a dynamic range from mezzoforte to fortissimo.
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