Chordex brings a wealth of musical chord knowledge to your desktop.
It offers two modes of operation.
The second mode allows you to highlight notes on a virtual keyboard, while the app lists the chords that contain those notes in an order based on both how well they match and their obscurity. For example, if you select D and F, it is fair to say that D minor is a better fit than A♭ diminished 7th, but both are options. Again, this mode lists the notes that make up each of the suggested chords and offers you the chance to listen to them all.