Free software chord plugin?

Wondering if anyone can suggest a freely licensed chord plugin? Ideally such a thing would allow me to hit a single note and present me with endless hours of chords to choose from. The selected chord would be audible (suggesting the plugin's MIDI output would be routed to the MIDI input of something that generates sound) and be displayed on a piano-ish layout so I'd be able to see what is happening.

Of course, some aspects of the above could also be incorporated in the plugin itself if it were capable of producing audio.

I had previously cobbled together a workflow involving Carla, Qtractor, and jack-keyboard but haven't used it in some time since it really didn't provide "options" in the way I'd like. In other words, I can only imagine a purpose-built plugin would be much more fun and useful to work with.

Thanks in advance for any suggestions.