I wanted to be shocked at "clean" and "motor driven generator" in the same sentence. But I fact-checked and it checks out. So have an upvote.
http://www.jkovach.net/projects/powerquality/
http://i21.photobucket.com/albums/b298/professor95/BrandY.jpg
While it remains true that cheap generators produce horrible sine waves, a good generator can be cleaner than the grid.
I am sure that a good motor/alternator can do 'electrically quiet' quite well, mechanically though its another matter and I think that you would have to be very committed to run up such a set every time you want to list to your stereo.
If we are going esoteric I prefer the idea of battery banks and then we can go straight in with DC and cut out the AC stage altogether, charge them during the day from PVs or from the utility and listen 'off-grid" during the evening.
If we are going to be radical we could use fuel cells run off Methanol or Hydrogen and once we had got over the initial and substantial CO2 cost for making the thing all that emits at (point of use) is water, Eco stereo :0) I agree probably not!