I`m getting confused on this. Is a note number, like say the lowest E that can be played on a specific instrument E1 and the next E up, E2 and so on? If so then does it depend on the instrument e.g. E1 on a clarinet would be different staff line E to tenor sax E1?
Or is the note numbering related to a keyboard and universal so that perhaps middle C (or lower) is C1?