Números romanos

Understanding Chords in "Threesome"

So, as you discover, the chords in "Threesome" are all white note triads: C, F, and G. Now, they're all in the key of C, which itself is composed of white notes.

Chord Numbers

We could give them numbers according to their position in the scale:

• C can be I (1)
• F can be IV (4)
• G can be V (5)

Based on the fourth and fifth notes of the scale, when we use Roman numerals like this, we're not talking just about a note; we're talking about a chord.

• We call F the IV chord in the key of C.
• G is the V chord.

In classical music, you'd call the I chord the tonic, the IV chord the subdominant, and the V chord the dominant.

In jazz and blues, we tend to use 1, 4, and 5 in preference to those terms, but they mean exactly the same thing.

Chord Chart Analysis

Let's look at a chord chart for "Threesome." You can see:

• There are two bars on the I chord (C)
• Two bars on the V chord (G)
• The next line starts on the V chord again and goes back to I with a brief detour to IV (F)

The B Section

The B section starts on the IV chord, repeats with a brief detour to I again, and then the F# triad in bar 22 is a chromatic link between IV and V.

The last chords, the F triad and the G triad, should be recognized as second inversion shapes with the fifth on the bottom.

The Perfect Cadence

Built into "Threesome" is a really, really common chord sequence known as a perfect cadence, which we find in all Western music.

Basically, that's a V chord followed by a I chord, like G to C.

• Notice how the root goes up a fourth (5 to 1).
• The root could also go down a fifth.

It doesn't matter whether you go up a fourth or down a fifth; when you have that root movement, we're dealing with a perfect cadence. In this case, that's V to I in the key of C.

You have it several times in this piece:

• First of all, when it goes from G back to C in bars 6 and 7.
• Also at the end of the bridge, it ends on the V chord and goes back to the I chord.

The Benefits of Roman Numerals

So, thinking in Roman numerals like this makes it easier to view relationships between chords because you're not just dealing with a key.

It helps you learn things in other keys or in all keys. In fact, if you start thinking in Roman numerals, it makes it much easier to transpose to other keys.