The Number System

There is a system in music theory, which can identify each chord in a key by a number, or Roman numeral. Learning this system is essential for getting session work in a studio, and Nashville studios in particular. This method, known as The (Nashville) Number System is a shorthand (just like tablature) for writing the music language. For starters, you need to know that every note in a major scale, has a chord that goes with it. So, let’s look at the “diatonic chord sequence” for the key of C major: C major, D minor, E minor, F major, G major, A minor, and B diminished (for the purposes of this article, I am assuming you already know these chords. If not, check out some of the piece in the Guitar Noise Beginner’s Theory page, like The Power Of Three).

Next, we are going to “code” these chords by changing them to a “number.” Using the key of C major, once again, as our example, we would convert our chords like this:

C=1, Dm=2, Em=3, F=4, G=5, Am=6, and Bdim=7

Music theory uses these numbers to describe the “position” of a chord, in the context of its particular key. So, in the key of C, a “1-4-5-6” chord progression would be the C, F, G, and A minor chords. Easy so far? Oh yea!

One of the reasons why this method is used is because you might find yourself in a situation where you might have to “transpose” a song. Transposing a song means, playing it in any key that is different from the one in which it is written, or the one in which you originally learned it. Therefore, transposing is much easier when you know the number system.

The secret to understanding this method, is realizing that the sequence of “chord types” are the same when transposing, whatever key they are played in. This means, in the key of D, a “1-4-5-6” chord progression would be the D major, G major, A major, and B minor chords. Just like we did in the key of C, we used this numbering method to “code” the chords.

By learning the notes in all twelve diatonic major scales, as well as the chord sequence, transposing or reading a chord chart becomes easy. Of course, anything new requires practice, and patience! Remember, the relationships between the individual chords described by the sequence of numbers remain the same, and only the actual pitches will change. Just like we did with the key of C and D examples. By the way, diatonic means notes that are “true” to that particular scale.

If you know how to form barre chords, play a G major barre chord with the root note on the sixth string/third fret. Next, play a B minor barre chord with the root note on the fifth string/second fret. This will be the “1” and “3” chords in the key of G. Now, move these two “shapes” up the fretboard one whole step. Once you’ve moved these two chord shapes up one whole step, you will now be playing the “1” and “3” chords in the key of A. These two chords in the key of A will now be the A major barre chord and the C# minor barre chord. If you were going to “transpose” a song in the key of G, with a “1-3” chord progression, to the key of A, again with a “1-3” chord progression, this is one way to go about it. Remember that music and math are closely related. Maintain your chord shapes, and compensate for open string chords. Having fun?

Now, what if you were in a Nashville studio, and were given a chord chart labeled “Country Ballad Demo”: (key of E) Intro: 1-6-4-5-1 (2x), would you know what to do? Easy, just remember your chord sequence for the (major scale); first identify what the 1-6-4-5 notes are, then identify and associate the correct chords that are placed with those numbers.

Here is your chord sequence for the key of E: 1=E major, 2=F# minor, 3=G# minor, 4=A major, 5=B major, 6=C# minor, 7=D# diminished. Now you can find what your demo “intro” will be; (E, C#minor, A, B, and E: “1-6-4-5-1”.) The (2x) means that you you play the intro chord progression (you guessed it) twice. The tempo and all other elements of the song would be outlined at the start of the session. This is a general idea of what you could expect in a recording studio. Also, when performing onstage, it is common to use chord charts with The Number System in some bands.

As we have seen, learning The Number System involves counting the number of steps up the major scale. The numbers are there to identify where the chords are positioned in the scale, and the chord types. Two main reasons that you would want to transpose a chord progression are: to find a good key for the vocalist, and to find the best fingering for a riff or chord shape. When you transpose a chord progression to the most appropriate new key, you’ve just solved your problems. Learning and mastering barre chords is essential for making everything easier on yourself. It is so much simpler to move a barre chord because your fingering stays the same. If you don’t have one already, get a book on barre chord shapes and general music theory. This will be very helpful in the speed of learning.

Here is an example of some of the things you would study in music theory. “As far as learning about chords, there are four different triads to study. (A triad is a combination of three notes played together.) Here are the four triads: major, minor, augmented, and diminished. With any given triad, when you change the order of the notes, it is called inversion. Any one of those three notes could hold the root position. With every triad there are three inversions; root position, first inversion, and the second inversion. With each inversion you will have different sounds, and what I call the “mood” of the chord.” Confused yet? It gets easier with a good detailed book. The best thing to do is take one area of study at a time. Remember that learning The Number System and knowing your chords go hand in hand. So a good place to start in music theory is chord study.

I like to give a basic outline of a lesson, and let you discover the rest. I think it’s more fun and rewarding when you discover something on your own. It can take a little longer, but it will make you a better musician. You will have to spend more time on the subject, and put in more practice and thought, but as mentioned the rewards will be greater!

Have fun with everything you learn, and always try to apply what you’ve just learned to your older lessons.

About the Author

Jimmy is a working musician in a country/classic rock cover band. He has been playing guitar since 1979, and started in his first band in 1981. Having taught guitar for over eight years in several music stores, he still considers himself a student and loves the idea of learning. He was awarded a scholarship to the Atlanta Institute of Music, and has appeared in two different guitar magazines: Guitar FTPM, and recently in Guitar Player. His idea of success is making a living doing what you love, and being a good provider.For more on Jimmy, please visit his website.