I decided that while the coloured vinyl was ok on its own, the addition of a coloured note was just too garish.
The anti-aliasing round the note needs tweaking, but I think it looks pretty good. Better than the original:
EDIT: OK, I’ve tweaked it. Here’s the final version:
For Mac users, there’s a zip of those designs I got as far as making into .icns files here. To change the iTunes icon: rename whichever icon you prefer as ‘iTunes.icns’. Then you need to quit iTunes, right-click it in the Finder and choose ‘show package contents’. In the ‘Resources’ folder, replace the original iTunes.icns file with your new one (but save a copy of the original somewhere just in case).