I needed a way to make short and easy to understand notes for some songs. I started to use the roman numerals and key signature method that you find in music theory books. Then someone told me this was called The Nashville Number System. After using it for a month it seems to really have improved my understanding of theory. Plus I can make a chord chart for 40 songs on two sheets of paper. Example Bm: Vr(i vi VI v) Ch(i iv v). Its more like a cheat sheet than a real chord chart. I was wondering if many people used this notation.