On Key app for iPhone and iPad

On Key will help tune your stringed instrument with two different modes:
- Listen Mode will use your devices microphone to actively listen to your instrument, and tell you if each string is in, or out of tune (now with support for external inputs, like iRig).
- Play Mode will play a tone from your devices speaker, so that you can manually adjust until you are in tune.

Currently Supported Instruments:
- Guitar*
- Guitar (7-string)
- Bass*
- Bass (5-string)
- Violin
- Viola
- Cello
- Ukulele (standard soprano)
- Banjo (standard plectrum)
- Banjo (5-string)

* Includes alternate tunings, such as Drop D and E Flat