 So, the chord progression codice_1 in the key of C would correspond to codice_2 in Nashville notation, while codice_3 in the key of G would also become codice_2.This method of notation allows musicians who are familiar with basic music theory to play the same song in any key, as does Roman numeral analysis.In some European countries (France particularly), pop and jazz musicians often use so-called "chord grids" that show in a graphical way the chord progression.