On the kinematics of spiccato bowing

A skilled string performer is able to play a series of spiccato notes (short strokes played by a bouncing bow) with each onset showing little or no aperiodic motion before a regular slip/stick pattern (Helmholtz motion) is triggered. Kinematic analysis reveals that a well-behaving bow gives nearly vertical impacts on the string, and that the first slip of each note takes place when the normal bow force is near its maximum. The complex movement of the bow stick can be decomposed into a translational and a rotational motion. Within one full cycle of the translational motion (down-up bow), giving two notes, the bow describes two periods of rotational motion. The axis of rotation is close to the finger grip at the frog. This paper discusses the relation between the quality of the spiccato and the phase lag between the two components of bow motion.