Pitch measuring accuracy much higher then usual software tuners based on fast Fourier transform (FFT). This software use special algorithm instead of FFT. Acoustic guitar strings tuning. High precession note pitch measuring. This simple software determining exactly pitch of your guitar strings, by using microphone and sound card. You can try it free of charge even without microphone. If you think you can tune your guitar exactly using only reference tones, you are poorly wrong. Theoretically, when you are using reference tones and the frequencies are roughly the same, a great resonance is produced. In this case reference tone become a source of forced oscillation, which cause strings oscillation on the same frequency. And it sounds like guitar is tuned. But actually own string frequency can greatly differ from reference tone. That's why preferably to use passive system which only listen and does not provide any sound oscillations.