This is a professional Tuner for Violin, Viola, Cello and Violone(double base, double bass).
We have been focused on musical instrument turning for more than 10 years. We designed and manufactured a large number of popular professional digital tuners, as the upgrading and replacement, we recommend this App.
It's very easy to use, pluck a string of your Violin, as the sound enters the mobile phone, App will accurately identify the string and the deviation of frequency in cents.
App only responds to musical tones in certain frequency range, while filtering out other interference sounds.