Although extensive research has been conducted over the past two decades on the development and implementation of sensors using inertial movement units for violin bows, most of these new interfaces share a common drawback—bulky and user-unfriendly design. Despite the advancements in sensor data processing for composition, performance, and pedagogy, interface design remains a critical bottleneck for the real-world implementation of these sensor-embedded devices. Our study introduces MetaBow, a low-cost, nonintrusive frog design for violin bows that can accommodate either a standard sensor kit or a custom-designed board. This interface eliminates the need for additional physical training and maintains the integrity of traditional violin performance mechanisms. We thus view MetaBow as heralding a new era in digital music interface design for the violin family with the potential for seamless human–computer and human–machine collaboration in music practice and performance.