Sonic Effects of Bow Force Vector Differentials on Bowed Stringed Instruments

This study aims to develop a more objective framework for assessing tonal attributes perceived in violin family instruments based on specific variations in the bow’s “roll” angle and bow force vector direction. In this study, two bowing techniques are juxtaposed in which musicians employ two specific methods of varying the bow force vector angle on instruments of the violin family. These two methods consist of 1) Technique A, in which the musician directs the bow force vector perpendicular to the string on 8 test pitches, and 2) Technique B, in which the musician directs the bow force vector at an increasingly acute roll angle in relation to the bridge on the same 8 pitches. The comparison of the tonal attributes in the contrasting bowing techniques is achieved by 1) an objective correlation study in which FFT graph overlays and roll angle data are gathered and analyzed from an audio/video recording of four musicians using both Techniques A and B, recorded on a set of 8 test pitches along with a synchronized recording of the bow’s roll angles, and 2) a blind qualitative survey study in which participants use a tonal spectrum chart to assess their perception of the contrasting techniques on 8 test pitches played on the double bass. The results for the objective correlation study overall exhibited a positive correlation between the use of Technique B and increase in decibel level in the FFT analysis of the test pitches recorded on each of the four instruments of the violin family. The qualitative survey study resulted in a positive correlation between use of Technique A and tonal descriptors such as “spread,” and “hollow,” whereas Technique B was positively correlated with descriptors such as “focused” and “projecting/strong.” While these findings are not entirely conclusive, the data suggests promising trends in the tonal properties attributed to the two bowing techniques. Due to the limitations in the ability to control numerous bowed instrument parameters, further research is necessary to support the conclusion that these bow force vector variation techniques directly yield the results obtained.