I'm writing a piece of music for a bass player that has a 5 or 6 string bass (Using PrintMusic 2010). I'm seeing negative fret numbers on the program. For example, when I enter ledger notes below E natural (4th string), is when I began to see the negative fret numbers. What do they mean? I am assuming, unless you do it by hand, that most music programs does not allow you write a tab for 5 or more strings.