When is it appropriate to use "sul ponticello" in a performance?

Using "sul ponticello" is appropriate when you want to produce a bright, thin sound on stringed instruments. This technique involves playing close to the bridge of the instrument, which creates a unique and ethereal timbre that contrasts with the fuller sounds typically produced when bowing further away from the bridge. The resulting tone is often characterized by its delicacy and transparency, making it suitable for certain musical passages where a more ethereal or shimmering effect is desired.

Clarity, richness, and vibrato are achieved through different techniques and positions of bowing. For instance, clarity might be pursued through more direct bow strokes, and a rich sound is generally the result of bowing with a fuller stroke closer to the fingerboard. Vibrato involves the left hand's manipulation of notes rather than the bowing position.