Guitar Theory: Roman Numerals

Just a quick post on how we use Roman Numerals in music notation. In music, you’ll sometimes see things like: “V7 – I”, “ii – V – I” or “I – IV – V”. Just what do they mean?!

Well, lets look back at how our scales are numbered:


1 2 3 4 5 6 7
C D E F G A B

If you haven’t yet read How to Harmonise a Scale I suggest you go and do that now, because what I’m talking about relates to that.

For some reason, musicians like to use Roman Numerals instead of the usual Arabic ones to represent the chords build off each note in the scale, so that gives us:


I II III IV V VI VII
C D- -E- F- G A- -B-


…but that’s only half the information! We don’t anything about the types of chords we’re looking at. That’s why we use capital letters for major chords, and small letters for minor chords. This makes our major scale look like this:


I ii iii IV V vi vii°
C D- -E- F- G A- -B-


Capital numbers are major chords, and small numbers are minor chords. The little “°” signifies a diminished chord.

WHY?!

This system is good because we can talk about chords and chord progressions without actually having to refer to a particular key. For example, if we talk about a “ii – V – I”, in C those chords will be: Dm, G and C…but we could also apply it to the key of G (Am, D and G) or A (Bm, E and A) or any key we wanted to, because we have all the information there except which key it’s in (making it more useful for talking “in general” about chords or keys).

I hope this makes sense, if not there is a comment section below…
Rob.

January 28, 2011 at 8:00 am | Music Theory | No comments