  However, I've also seen recent editions of duets that print Primo on the right and Secondo on the left. These recent editions have made improvements from horrible, older editions in these ways: 0) the editors have clearly labeled measure numbers instead of the dumb rehearsal "letters,"0) each system (between Primo and Secondo) starts on the same measure in the music, 0) the print is large and clear, and0) there is a lot of margin and space between systems in which to pencil in rehearsal notes.  