I'm discarding the LSB, it is on my code line where says "midi adjust" on READ0:.

Erik is right about discarding the LSB, it helps but dont solves.

I think making what Hans said (like a deadzone) will fix the problem. I feeding the project from batteries, can I feed it directly from MIDI port? (dont need batteries or ac adapter anymore).

I'm leaving VREF open, what is vref, and should I have something connected to this?

What do you think about my circuit, it is right? Its my first microcontroller project, please i need you tell me what you think about it (good or bad) or how to improve it. I just dont put it on a PCB because im not satisfied with it.

What do you think about delay time I'm using between end of conversion - input port change - start of new conversion? May I decrase it?

Thanks for help.

PS: Forgot to say, I will try "deadzone" soon as possible, and post results.