Use your ears, not your eyes, to improve your intonation!
Many of us traditionally practise intonation using a tuner, or perhaps a more sophisticated graphing tuner. In real world playing, though, you have to correct your intonation based on what you hear, not what you see on a tuner display.
Intonation Doctor gives auditory feedback for use during your intonation practice sessions. You play a note, and if your intonation is a little off, Intonation Doctor plays the correctly pitched note along with you. You get instant feedback on what you played, as well as the target pitch you were aiming for - using your ears.
You're free to close your eyes and immerse yourself completely in the sound and feel of what you're playing. You're attention is no longer directed towards processing visual information.
Intonation Doctor is intended to be used in slow, deliberate intonation practice. The best way to practise intonation is to vividly imagine a target pitch in your mind's ear and then try to reproduce that tone exactly on your instrument. The app isn't designed to accompany fast playing.
Intonation Doctor plays target pitches using a piano timbre.
If you're able to use external speakers, it may be easier to achieve the right volume balance between your instrument and your iPhone, iPod touch or iPad.
You'll need an external microphone if you're using an iPod touch 3rd Generation or older.
Intonation Doctor has been designed for instrumental practice and isn't currently suitable for singers or vocalists.