Sentence:  That is , when Mr. Milstein thrust straight to the core of the music , sparks flying , <WSD>bow</WSD> shredding , violin singing , glittering and sometimes spitting , Mr. Hendl could go along . 
Meaning of the word marked with <WSD> tags:  a slightly curved piece of resilient wood with taut horsehair strands; used in playing certain stringed instruments