A self-contained tuning stabilizer for a stringed instrument consists of a body which is attachable to the stringed instrument like a capo, the stabilizer containing mechanical members for increasing or decreasing the tension on each of the strings to keep them in tune as the instrument is played. The device contains sensors for each string, an analyzer for determining if the frequency produced by each string is correct, and a driver for each of the mechanical members for applying micro-tuning corrections to the strings. The device must first be zeroed, and the instrument tuned by hand. Thereafter, the device will maintain the original tuning.