The Violinist's Sound Palette: Spectral Centroid, Pitch Flattening and Anomalous Low Frequencies

The string player controls variations in spectral content mainly via bow velocity, bow-bridge distance and bow force. Many combinations of the bowing parameters influence the pitch noticeably as well, in particular close to the upper bow-force limit in the Schelleng diagram. The influence of the bowing parameters on the spectral content and pitch were studied systematically by use of a monochord and a bowing machine. Bow force was found to be by far the most dominant parameter determining the spectral centroid. Bow-bridge distance and bow velocity serve essentially as indirect control parameters of spectral content by giving the player access to playable areas with high or low bow forces in the Schelleng diagram. Clear areas of pitch flattening could be distinguished below the upper bow-force limits in the Schelleng diagrams, confirming the role of pitch flattening as a practical bow-force limit in playing. The conditions for anomalous low frequencies (ALF), S-motion and other, higher types of string motion were analyzed, and it was shown that secondary waves might play an important role in their creation.