Here is a logo that works well in color or black-and-white. The icon also works well at low resolutions as a favicon. Let me know if you have any suggestions. Thanks, Todd.
#6 is a neat idea (notes on a staff make an "e" -- I think I'd prefer a logo with the symbol integrated into the name (so perhaps there's way to merge that "e" with the "MusicTheory", so that the whole logo is more a single integrated thing. I agree, it's a bonus that there's an easily separable favicon.
Another note: there should be no space between "Music" and "Theory".
Sorry! Apparently I don't see new messages from you unless I click back on your submissions. #13 is probably still the best of those; the italics serif font isn't working for me -- I think something still a bit quirky but sans, non-italic, and medium weight will be the best.
But I should also say that I think the concepts using the G-clef seem to be working out better for now. Thank you!