Ukulele 

ear training, sight reading, and music theory applied to piano, guitar, violin, viola, cello, and bass - MusicGoals offers study, practice, and testing to improve skills, gain knowledge of instruments and music theory, and train the musical ear. This......

ChordAlchemy offers a rich and robust set of capabilities for looking up chords, determining what chords you are playing and hearing how they sound.

Chord variations are easily handled by ChordAlchemy's powerful, Advanced Chord Theory and Chord......

 Ukulele