Really good voice modifying app for iPhone?

Okay I'm a singer but I need an app that allow you to modify your voice like if your an okay singer it will change it to an amazing singer and if you suck then you turn out to be okay. And please let me know if you can somehow get the modified voice out of the app like you can add it to iTunes or email it.

Ahh… Sends me right back to my days as a sound engineer. Standing behind a rack with $65, 000 worth of equipment and having someone ask me "Can you make me sound better?" Being a good singer is about pitch control and vocal quality. There isn't going to be an app that can make you sing from your diaphragm rather than your throat and the pitch CAN be fixed a little IF you have a powerful app that knows what song you're singing and can sync up your singing with the song and THEN compare pitch.