Pitch Trainer - Harmonize is a music app designed to help users develop perfect and relative pitch. It is especially useful for those learning the chords of just intonation. This app is beloved by a wide range of users, from karaoke enthusiasts to members of brass bands and orchestras.

The app focuses on learning double-stop notes in just intonation. It plays two sounds simultaneously, and the decision is calculated based on just intonation. For example, when matching a major third "do" and "mi", there is a gap of 4 semitones in equal temperament, resulting in an interval of 400 cents. However, in just intonation, "mi" has a frequency ratio of 5/4 to "do", resulting in an interval of approximatelycents. This means that for the piano (equal temperament) interval, a minor adjustment of approximately -14 cents is needed.

The app provides a piano sound as a guide, but users are encouraged to match the tone of the sound by feel. The goal is to operate the app in a way that loses the beat, resulting in a sudden clear sound at a certain position, indicating the just interval tone.

Please note that the reference tone for chords in this app is A=442 Hz.