Hello!
Well, this may not be exactly what you are looking for, but I am also thinking about doing my own invites for my daughter's 2nd and I came across a site called smilebox.com. They really have super cute designs that you can print, email, save to disc for a keepsake, etc all with added music (not the ones you print of course).
I was actually thinking about doing cute printed cards to send out to all the kids and email the adults and grandparents the musical picture email invites.
Anyways, just thought I'd throw another option your way to explore.
Good luck!
:)
~ A.