A free program for Android, by Tuni Apps.

Guitar Tuni – Guitar Tuner is a free guitar tuner app that is a simple, intuitive, and easy-to-use tool for musicians. It can tune any guitar, bass, ukulele, or mandolin, and works on any device with a microphone. It is the perfect app for beginners, and can be used by professionals.

It is a chromatic tuner that uses your phone’s microphone to capture the sound of the string you are playing. It can detect the sound from a wide range of musical instruments, including guitars, basses, ukuleles, banjos, mandolins, and more. It is also designed to work with different types of strings, including standard, drop, and open strings.

Once the sound is detected, you can set the A4 frequency to any value between 420Hz and 460Hz. It is a useful tool for musicians to tune their instruments. It can also be used to tune any other string instrument.