QWERTY chord input

I was thinking it would be really useful to be able to input chords using the computer keyboard, besides typing them in. Some other programs have this sort of feature---Ableton LIVE, for example. In those programs it's mostly just an ersatz MIDI controller, which I suppose has it uses, but I've been playing an ear-training game called Ear Training Companion, and it's given me the idea of using keyboard shortcuts for harmonic functions (instead of pitches), which I think would work really well in conjunction with HN's functional-harmony palette.

To illustrate:in Ear Training Companion the space bar is the tonic, the semicolon key is the dominant, "D" is major sixth, "O" is tritone, and so on. It would be nice if HN users could specify whatever keymapping they want for the chord palette (preferably using some kind of template that would allow one to switch easily between different mappings for, say, writing in different modes.)

The main difficulty I see with this sort of feature would be the limitation on the number of buttons you can press simultaneously on a QWERTY keyboard. (Maybe you could press the keys for the chord notes in rapid succession, from lowest to highest, with the program grouping them together as a single chord?) With a gaming keyboard equipped with anti-ghosting you wouldn't have that limitation, of course.