Dear Sir,
I've just seen the project you've posted. I'm musician and I used to go to website like yours to look for tablatures for playing song.
About your project, I don't want to say that I'll do everything without any difficulties like other do but I want to tell you that websites you've provided use diffrent technologies. They use flash for piano and bass (just right click on it and you will see the flash player mark) and javascript and jquery for guitar tablature.
What I can promise is that I can make the bass and guitar editor from the same technology : "javascript" but I can't do the same for the piano. Just look at the design, piano is for partition and not tablature, so we need another technology for creating such diffrent visual. (I'll do it with Adobe Flash to, like the website you've provided).
For storing, as tablature is textlike (ref : "[login to view URL]", it's really simple to send it to joomla from user accounting. So there is no problem for that. For piano storing, it will be more complicated, I can't promise that I can do it but I will do my best, I've already an idea for reaching this goal.
My last word is : I'm a honest developer, I just say what I can do, that's why people trust in me. I've never accepted any money from person who is not satisfied from my work. So I really hope that I will work for you for this project.
Thanks & Best Regards.