Task: to develop an app on which you can tune an electric guitar, an acoustic guitar, a bass guitar and a ukulele. The app should be suitable for both professionals and amateurs. Solution: the tuner works smoothly, accurately, without jerking, which most apps have. There is an opportunity to apply different tunes in each tool , for example: standard, Drop D. The application can be seen from a distance because it has a contrast interface. You can successfully work in poorly lit rooms. There is a tuning fork for setting the instrument by ear.