Roman Numeral System

Roman Numerals in Diagrams Represent a Chord's Position in a Key

How to Write out Chords using the Roman numeral system

Roman Numerals in Diagrams represent chords in a key (or sometimes the root of the chord), based on the chords position in the key. We simply count the letters. So in C Major C=I, D=II, E=III, etc. Numbering is based on the major scale, so if a scale has a different note in comparison to the Major Key built on the same letter; we put a Sharp (♯) or Flat (b) in front of the Roman numeral to show how it differs from the major key. Then we put the symbol of the chords quality (i.e. Major, Minor, Dominant Seventh, etc.) after it. Once again, no symbol = Major.

Note: This notation system uses all uppercase Roman numerals. There is a second system (not used on this site) using upper and lowercase numerals that is, to be honest, far more confusing and I see it being used less and less.

How to Call out Chord Changes using the Roman numeral system

It’s normal in jams and rehearsals to have to inform other players of the chord changes to songs they may not know.To tell other players to switch to the chord built on the fourth note of the key (written as IV); we would tell them to “go to the four” maybe “go to the four chord.”Standard sequences of chords that players usually know and practice (for example E-7 A-7 D-7 G7 C) would be said “Three Six Two Five One in C,” with the assumption the players know what chords go there.E7 A7 D7 G7 C7 would be most likely be said something like “Three Six Two Five One in C, all chords dominant” because the usual chords have been switched. What the usual chords are in a given context can require quite a bit of work depending on your playing ability, but knowing the lingo/jargon is important because you don’t want to miss an opportunity to play with good players because you didn’t take the extra little time to memorize what things were called.

What to do If the Roman Numeral system Seems completely over Your head

Don’t worry about it!

Although it is used extensively in music theory (i.e. functional harmony, or common tone substitution), songwriting, transposition (i.e. switching keys so the singer can hit all the notes), and in intimidating less studied players, you can still play a great show or rock a campfire without it. But eventually you will most definitely want to have a grasp of it!

As you learn new chords off the Fretboard Diagrams, take a few extra minutes to memorize what their position is in the key (all chord diagrams on the site are grouped by key, and have the Roman numerals on them). It’s that simple (let’s be honest, remembering a number is way easier than learning chord forms as a beginner). Then when you need to know the advanced uses of them, you will already know what’s what in the keys you can play in.