Please note that this app has been deprecated in favor of gStrings, which has recently been rewritten from scratch; with a multi-core optimized engine, improved fundamental frequency detection, smooth OpenGL graphics, a redesigned UX, and a simplistic/focused material UI.
(!!) NOTE: this application is free to download, but will only work for a limited amount of time before you will have to activate it through a small one-time in-app purchase fee (~3EUR). Besides giving you a chance to try the app before you buy it, this was also the only way (due to technical constraints of the Play Store) to be able to give away this app for free to all existing gStrings users with paid content.
The app measures sound pitch using your phone's microphone, letting you tune any musical instrument (violin, viola, violoncello, bass, guitar, ukulele, piano, even wind instruments to name a few that have been tested).
1. orchestra tuning (shifting/redefining tone frequencies, e.g. A440 > A443),
2. different temperaments (pythagorean, bagpipe, etc.),
3. custom user-defined temperaments,
4. different note namings (English, Latin, Hindustani),
4. a nonlinear scale,
5. microphone sensitivity setup,
6. pitch pipe.
If you were looking for a guitar tuner, try gStrings instead!
Thank you note: most of the historic temperaments were included courtesy of NetCat AG.