How do sul ponticello and sul tasto change the tone of a bowed string instrument?

In the context of bowed string instruments, sul ponticello and sul tasto are performance directions that alter the instrument's timbre by changing the location where the bow contacts the string.12

• Sul ponticello: The player bows near the bridge. This technique emphasizes the higher overtones, resulting in a characteristic nasal tone.32
• Sul tasto: The player bows over the fingerboard. This technique produces a soft, thin tone.42

By varying the bowing position along the length of the string, the performer can significantly influence the tone quality, providing composers with a wider palette of sound colors when writing for string ensembles.12