by Conrad Albrecht
I wanted to explain a common set of chords called the diatonic chords. But to understand the diatonic chords, you first need to understand scales; and to understand scales, you first need to understand the 12 chromatic tones our music is based on. So this article will explain the basic theory of pitches in our music, including the 12 chromatic tones.
Each note in a piece of music has a pitch. The pitch is how "high" or "low" the note sounds. Between the lowest audible bass pitch and the highest audible treble pitch, there are thousands of possible pitches.
However, our music doesn't use all of these possible pitches. Pitches that are too close together sound "out of tune" to us, so our music doesn't use them and we don't have names for them. The pitches that we actually use and give names to are a series of pitches called the chromatic scale:
The "chromatic ladder" on the left shows a section of the chromatic scale. Click some neighboring boxes in the ladder to hear what the half-step distance sounds like.
We use letters to name some of the pitches. On the right is that chromatic ladder section again, showing the letter-named pitches. Notice:
Why do we use the same letter over and over for different pitches? Because to our ears, a higher C (for example) sounds like "the same note, but higher" as a lower C.
Try playing two different C's (or D's, etc.) in the chromatic ladder to hear how they sound "the same, but different".
The distance from one pitch to the next pitch with the same name (e.g. from an F to the next higher F) is called an octave. If you count the half-steps in the chromatic ladder from one F to the next F, you can see that one octave equals 12 half-steps.
Often, when we discuss the notes in a scale or chord, we don't care which octave the notes are in, because they have a similar effect regardless of their octave. So we can say, for example, "the C major chord contains the notes C E G" without worrying about which C, E, or G we mean.
We still need names for the pitches in between the letter pitches, for example the pitch between G and A. These pitches don't get their own letter; to name them, we use a neighboring letter plus the sharp (#) or flat (b) symbols. The sharp (#) makes a pitch a half-step higher; the flat (b) makes it a half-step lower.
For example, the pitch between G and A can be called either G# ("G sharp") or Ab ("A flat"). By either name, it sounds the same. Sometimes one of the names is preferred over the other for music theory reasons, but we won't worry about that yet.
On the left is our chromatic ladder section again, finally with all the pitch names filled in.
When we talk about the notes in a scale or chord, we usually don't care which octave they're in. And if we ignore the different octaves, there are only 12 chromatic tones:
These are the 12 tones which we choose from to make scales and chords.
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