Friday was a noteworthy day at Day Job and included -- among other things -- a lunchtime round of Guitar Hero. (Don't ask.) I was very kindly asked to participate but
Then an Office Mate -- the same one who sold me his Asus Eee PC -- told me about Frets on Fire, an open-source clone of Guitar Hero. (You use your keyboard upended for the controller.) At least that covers my third concern.
Then I noted your can -- really, must -- upload your own favorite songs, in the open OGG format or as a MIDI. MIDI, really? Because most of the MIDIs I know of are hymns. And while that doesn't exactly address by first concern, it does mitigate it. (And it's a goofy enough idea to minimize the second concern.)
A pretend-guitar playing game, on open-source software, pretending to rock out, Folk Mass-style. First, I think that helps establish my geek cred. And it does make the mind wonder and wander.
For Linux of course, but also Windows and Mac OS X (wonky): Frets on Fire