sul ponticello explained
techniquessul pon-tee-CHEL-lo
A string technique in which the bow is drawn near the bridge, producing a thin, glassy, overtone-rich sound
Playing near the bridge (sul ponticello, on the little bridge) emphasises the higher partials of the harmonic series while suppressing the fundamental. The result is an eerie, metallic sound that is rich in overtones and poor in warmth. At extreme closeness to the bridge, the sound becomes scratchy and almost white-noise-like. Composers use sul ponticello for atmospheric and unsettling effects. The opposite instruction, sul tasto (near the fingerboard), produces a warm, flute-like tone by emphasising the fundamental.
Penderecki's Threnody to the Victims of Hiroshima uses massed sul ponticello playing from 52 strings to create a sound of almost unbearable tension.