A free app for Android, by Frankensound.

Songo is a free Android app which serves as a pocket chord-finding tool for musicians and songwriters. It is designed to be used with your Android phone or tablet, not a computer.

The app contains many different categories of chords, from the most important ones (I, IV, V, etc.) to the more obscure ones (Reger, Rossini, etc.). Each category can be sorted by the type of music (rock, pop, classical, jazz, etc.) or by the composer (B. Tellier, J. Schnablok, W. Ater, E. Lambert, etc.

In addition to that, the app contains a lot of information about the chords (the name of the chords, the key of the chords, the position of the chords in the song, etc.