This paper explores the potential of near-field optical reflective sensing formusical instrument gesture capture. Near-field optical sensors are inexpensive,portable and non-intrusive, and their high spatial and temporal resolutionmakes them ideal for tracking the finer motions of instrumental performance.The paper discusses general optical sensor performance with detailedinvestigations of three sensor models. An application is presented to violinbow position tracking using reflective sensors mounted on the stick. Bowtracking remains a difficult task, and many existing solutions are expensive,bulky, or offer limited temporal resolution. Initial results indicate that bowposition and pressure can be derived from optical measurements of thehair-string distance, and that similar techniques may be used to measure bowtilt.