C D E F G A B C

Listen to the C major scale.

You may recognise the sequence of notes as do - re - mi - fa - so - la - ti - do. Notice that the first and last note sound the same, except that the latter is higher in pitch. Both of these notes are called 'C', and they are said to be an octave apart, the word octave coming from the fact that the eighth step of the scale takes us back to the tonic or first note.

If we were playing guitar, we could play this scale entirely on the B string by playing at frets 1 (C), 3 (D), 5 (E), 6 (F), 8 (G), 10 (A), 12 (B),and 13 (C).

If we were playing this on a piano, we would just be playing white notes, starting with the white note C immediately to the left of the group of two black notes.

Diatonic harmony means using only the notes in a given scale to make chords. A chord is simply two or more notes played at the same time. Usually, musicians use chords containing at least three notes. The simplest chords, called 'triads', are made by a process called 'stacking thirds'. To make the C triad, we play C, then go up two notes to E (the third note), then up two more notes to G (the third note, counting from E as 1). Playing these three notes, C, E, and G, together makes the C major chord or C major triad. Listen to a C major triad.

Just as we made our C major chord by stacking thirds on top of the first note in the C major scale, we can build chords on each note, or 'degree' of the scale in the same way. The chords we make look like this:

CEG, DFA, EGB, FAC, GBD, ACE, BDF, CEG

Listen to these chords.

Let's look at the chords more closely. The distance or 'interval' between notes can be counted in semitones. A semitone is the interval between notes that are one fret apart on the same string on the guitar, or between two adjacent notes on the piano keyboard, such as C and C# or E and F. A tone is an interval of two semitones.

If you look at a piano keyboard, C and D are a tone apart, because there is a black note called C sharp/C# or D flat/Db) between them. B and C have no black note between them, and so are only a semitone apart.

The intervals in a major scale look like this:

From note I to note II = 2 semitones (a tone)
From note II to note III = 2 semitones (a tone)
From note III to note IV = 1 semitone
From note IV to note V = 2 semitones (a tone)
From note V to note VI = 2 semitones (a tone)
From note VI to note VII = 2 semitones (a tone)
From note VII to note VIII = 1 semitone

Notice that the eighth note is the same as the first note. Also, be aware that Roman numerals, as used above, indicate which note of a scale we are playing as the root of a chord. If we are playing a piece of music in the key of C, we might refer to the chord CEG as our I (one) chord, and the chord GBD as our V (five) chord. (Roman numerals are used to avoid confusion with chords like G7 - note the Arabic numeral 7 - which is a four note chord containing the notes G, B, D and F. We will look at chords containing four or more notes later on.)

Looking at our C major triad in terms of intervals, we see that from C to E is an interval of four semitones. This interval is called a major third. Continuing from E to G, there is an interval of three semitones, called a minor third. So, the C major triad is made of the notes I, III and V in the scale of C major, or a major third (C to E) with a minor third (E to G) on top. The V note, G, is seven semitones above the I note. This interval is called a perfect fifth.

Now look at the next triad, formed from the second degree of the C major scale. This triad contains the notes D, F, and A. Listen to this chord. The interval from D to F is three semitones (a minor third) and the interval from F to A is four semitones (a major third). So this chord is similar to the C major chord in that it contains a major third and a minor third interval, but different because in this chord, the minor third interval is on the bottom and the major third is on the top. Chords built like this are called minor chords, and this one is built on D, so it is called D minor. You could make the D minor chord by playing the first, third and fifth notes of the D minor scale.

If you play this chord, you should notice that it has a sad sound. All minor chords have this sound.

You can see that the fifth note within this chord, A, is seven semitones or a perfect fifth above the root note, D - just as the fifth note in our C major chord was a perfect fifth above the root note. The only difference in the pattern of intervals is with the third note, which is one semitone lower, or 'flatter' than the third note of the major chord, relative to the root note. Musicians sometimes refer to this note as a 'flattened third'.

To make this even more obvious listen to a C major chord compared to a C minor chord. The C major chord contains the notes C, E, G: C minor contains the notes C, Eb (pronounced "E flat"), G - it is not a diatonic chord in C major because the note Eb does not occur in the C major scale. You should hear that the flattened third changes the character of the chord from happy to sad.

When musicians play chords, they don't just play the triads as described above. The three most common ways of playing a C chord on the guitar are like this: CEGCE, CGCEG, and CGCEGC. So long as a chord contains the notes CEG and nothing else, it is a C major chord. Note that the lowest note is usually the root note of the chord.

In Part Two, we will go on to look at the other triads that are built on the major scale, and how they are used in music.