Tl;dr Ear Sharpener is the best app for learning relative pitch. Visit earsharpener.com to try it out for free.
Beginners: Train to have musicians ears. The first level is easy to pass, even for a non-musician. From there, difficulty increases in baby steps.
Musicians: *Every* musician will find an Ear Sharpener level that is challenging and edifying for them. Theres no "unlocking" of levels, so navigate through the levels to find whats right for you, or create your own custom levels.
Ear Sharpener is an intense but simple game that trains you to hear whats happening both melodically and harmonically in music - whether youre listening to something thats playing on the stereo, at the club, or in your head.
How To Play:
Youll hear a cadence in C (a IV-V-I), and then a random note. You indicate what note you think you heard. Once you get it right, youll be presented with another cadence and random note, repeating until you pass the level.
To pass a level, you need a streak of 20 correct answers, and each answer must be given within one second of hearing the note/chord.
For Beginners: Rather than diving right into all 12 notes, the first few levels are incredibly easy - in the first level, for example, you have to distinguish between just the notes C and G.
If you already have a pretty good ear: Start with the last exercise under "Beginner / Notes I". The note recognition will be easy for you, and youll have a chance to get used to how the game works.
Eventually, youll progress in baby steps to all the diatonic notes, and then all twelve tones, and then through a gradually widening note range (whereas at first, the notes are restricted to the Middle-C octave). At that point, youre in a pretty good place, ear-wise, but you can further increase your skills with multiple-simultaneous-note exercises.
There is a similar baby-steps path for triads, where you are identifying the root, starting out with root position C and G chords, and ending with triads in various inversions in various voicings built on all twelve tones.
Ear Sharpener comes with 140 preset levels, but also gives you the ability to design your own custom levels, where you can change the cadence keys, or have the app randomly change the cadence keys, or opt to not hear the cadences at all.
Here are some notable things that this app *does not* work on:
Chord qualities: The app will play you major, minor, augmented, and diminished triads, but it only cares whether you can identify the root.
Intervals: Ear Sharpener doesnt deal with the vocabulary ("major third", "perfect 5th") used in interval training. Interval training helps you to identify the "distance" between two notes (pretty useful), whereas Ear Sharpener will train you to hear notes in the context of some specific tonal center (much more useful).
Playing with friends: There is no replacement for the lessons you will learn by getting together with your friends and improvising music on a regular basis.
For questions or support, write to [email protected]