Piano Companion is a music theory app for songwriters, producers, teachers, and students. It’s a flexible piano chord and scale dictionary with user libraries, reverse mode, circle of fifths, and a chord progression builder with common patterns. If you can’t remember the name of a piano chord or scale, this app will help you to find it by key or using your external MIDI keyboard. For example, just press C and G, and you will get C Major as the first piano chord in the search result. If you don’t see a piano chord or a specific scale, you can create a custom piano chord or scale and use it for chord charts or your user library.