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Music theory and the number system

Hello my reso friends. With this blog I’d like to talk about the topic of the number system. Some of you may have heard about this, and I’ve done some here and there to describe it. What I’ve noticed is that with music theory type stuff, it takes a lot of repetition over time and from different angles for things to sink in. So let’s use this as an opportunity to push the bar forward a little on our knowledge of theory, and more specifically, the number system. It’s a pretty useful and widely used way to refer to notes or chords, and help musicians communicate.


So you may have heard people refer to “the 1 chord”, or “the 4 chord” and so on. You may have heard some tell you the chords to a song in this way. For example, “the chords to this song are 1, 4,  5”.  We’re going to discuss what that means and how you can use it. Let’s start by using the key of D for our example. The notes in a D major scale are, D E F# G A B C# and D again. The D note here is called the tonic or root note. Pretty much the home note that the whole key is organized around. One way we know to refer to these notes is in solfege. Do Re Me Fa So La Ti Do. Basically each note has a name. That is a moveable system. If you use a different major scale, besides D, the first note is still referred to as Do, the next note Re and so on. Now what many musicians use instead of Do Re Me, is actually a number system. So in the D major scale we’re using, D would be 1, E would be 2, F# would be three and on like that up to 7. The octave of D would be 1 again. 


Now you can use these numbers not only to refer to single notes, but to chords. So if I want to play the 5 chord in the key of D, what chord would it be?

Well you can just count up from D, 

     D E F# G A B C#. It’s an A chord. The 4 chord in D? G chord.    

     1 2  3   4  5 6  7                                                                                                                                                                                                                                                                                                                                            


Now there’s one more step you need to know. Not all of these chords are major. Some are minor, and one is diminished. But don’t let that scare you. I’ll list them here and this is a good thing to memorize. But I’ll also explain why this is. 

1   Major

2   Minor

3   Minor

4   Major

5   Major

6   Minor

7   Diminished


So if we’re in the key if D, and someone says play the 6 chord, and they may even say 6 minor, what chord do you play? Take a look up at the numbers. It’s B minor. If they say play the 2? If we’re sticking to the rules it would be E minor. Now why are some major and some minor? (This is getting deep I know. It’s not a bad idea to have your Dobro around to investigate some of this first hand. You can quit here if you want. This is a good chunk. For the brave, please continue.)


Well it’s because basic chords are built with 3 notes. Ok here’s where it can get a little confusing, but you’ll get it. The notes of a chord also use numbers to refer to their structure. The root of a chord, the third, and the fifth. So a D major chord has D, F# and A. D is the root of the chord, F# is the third, and A is the fifth. Easy right? Now the 2 chord in the Key of D is E minor as we can see from our little charts up above. The notes of an E minor chord are E, G and B. You can start to see a pattern here of how we build chords in a key. 

          E      G    B  C#        D     F#    A      C#

      D     F#     A                     E      G      B


      D major chord                E minor chord 


The notes of an E minor chord can also be referred to as the root 3rd and 5th of THAT chord.  So if someone says play the third of a chord, it may not be the third of the KEY. Unless it’s a D chord. : )

Really it’s ok if this all doesn’t sink in. Just let it gloss over you and it’ll come. Absorb what you can. 


So we still haven’t figured out why  D  F#  A is a major chord  and  E  G   B is a minor chord. This is where it’s helpful to have your dobro handy.  The note that defines wether something is major or minor is the third of a chord. The space between a D note and an F# note is two whole steps, or 4 frets. Play your open D string, then play the 4th fret F# note. That’s a major third. That interval has a certain flavor and we call that major. Kind of a happy sound. Now play the second fret 4th string E note. Then play the 5th fret G note. only 3 frets different there instead of 4. 1 whole and 1 half step. That’s makes a minor sound. A little plaintive or sad. That’s minor. So the difference in frets or steps between the root and third of a chord defines if it’s major or minor. These intervals happen naturally in a scale. 

                                    E             G        B     C#                  D           F#       A      C#

                              D          F#         A                            E           G         B

                                  \    /                                                  \       /

                              2 whole steps                             1 whole 1 half step

                               or 4 frets                                         or 3 frets

                                 Major                                              Minor


You can keep pulling out 3 note combos from the D scale and see what chords they make.   D E F# G A B C#    Just remember, there is a number associated with each scale degree, but also a root 3rd and 5th of each chord, and they’re separate things. So the reason we want to know all this stuff is because if someone says play the 6 minor chord, we want to know what that means. Now you can just memorize this if you want 

1   Major

2   Minor

3   Minor

4   Major

5   Major

6   Minor

7   Diminished


That’s a great start. But digging into why all this is the way it is can be helpful for you knowledge. And knowledge is power! That’s probably enough for this blog/lesson. Go forth and play 6 minor chords!


Thanks for reading guys. Let me know if you have any questions.