pick-guard; protective patch
A protective patch, often made of leather or similar material, attached to the body of a shamisen or similar stringed instrument to prevent damage from the plectrum (撥).
The pick-guard on my shamisen has worn down, so I replaced it with a new one.
Compound of 撥 (bachi, 'plectrum') and 皮 (kawa, 'skin, leather'), referring to the leather patch that protects the instrument from the plectrum. The reading ばちかわ is a straightforward combination of the two elements.