Defining the Key of G Major (and an introduction to modes)

Below is a summary of the key of G major. A key is defined when we create chords from a scale by stacking thirds on top of one another. A third spans three alphabet letters (e.g. G to B, or B to D).

The G major scale is diatonic, in that each of the seven letters of the musical alphabet appear in order, and the scale formula (the distances from one note to the next) will contain five whole steps (two frets) and two half steps (one fret). The F# in the scale is to ensure there is a whole step between the 6th and 7th scale degrees (the numbers written above the notes) and a half step from the 7th back to the tonic, G. The sound of the major scale is created by the whole-whole-half-whole-whole-whole-half sequence.

We commonly use Roman numerals to define the triad chord qualities in a key. Upper case numerals representing major triads, lower case for minor triads and the degree symbol (°) is added to the lower case numeral to denote a diminished triad (found on the 7th scale degree of the major scale).

Triads contain three notes, and we add an additional third above the fifth of the triad for a seventh chord. Note how not all the major triads are major 7th chords. The seventh chord created from the fifth scale degree (which can be named the ‘dominant’) will be a dominant 7th (R-3-5-b7).

The modes at the bottom are also all diatonic scales in that they will contain the same notes as the G major scale, but the tonic is a note other than G. For example, the C lydian scale would be the notes:



The mode contains the same notes as the G major scale (which is often termed the ‘parent major scale’ of the mode) and so it will also contain the same chords, but the order will be different:



My theory course ‘Guitar Rut Busters: Essential Theory’ goes through major scale theory in detail and shows you how the chords (triads) in a key are defined. Seventh chords and modes will be coming in the next instalment!

G Major Key Chart.png

F#? Bb? Confused by key signatures? This lesson will help

After a long break I'm back filming videos (and posting on this blog!) and I thought it time to continue my 'Guitar Theory' course - practical music theory for guitarists to better understand the instrument and music more generally.

This week's lesson concerns key signatures.  This refers to whether the music we are playing contains any sharp or flat notes.  This will depend on the 'key' we are playing in, which in turn depends on which scale the music is using because chords in a key are derived from scales.  That's for an upcoming lesson but for now...

To date we have discussed the major scale and how it is played.  We had a major scale if we were to play one octave of the C major scale (CDEFGABC).  If we list the distance from one note to the next we had the major scale formula (Tone-Tone-Semitone-Tone-Tone-Tone-Semitone). 

The C Major Scale played horizontally on string 2.

The C Major Scale played horizontally on string 2.

If we move the first note (or 'tonic') away from C and play one octave of the musical alphabet starting from, for example, the note G (GABCDEFG) we no longer have the sound of the major scale.  Why? Well, because the major scale formula only works with the musical alphabet when we start on C. Starting on G gives us this:

One octave of the musical alphabet starting from G...NOT a major scale

One octave of the musical alphabet starting from G...NOT a major scale

The video lesson below will explain how we can resolve this problem to be able to play a G major scale or any other major scale.  Yep, you guessed it!  We need some sharp and flat notes.