update 2017/07/16

came to be able to purchase a tuner mode in application.

TuningToneForViolin can detect four strings at the same time.

It's easy to operate, even while holding a musical instrument.
I think for other frequencies does not include pure sine wave, swell of sound of double-stop shifted even a beginner is felt, and can be tuning well.
G Sound of the sine wave so difficult to hear in the built-in speaker, please try "octave" the (sin wave).

Calculation formula
A = Setting
D = (A * 2)/3
G = (A * 4)/9
E = (A * 3)/2