2-1 · The Major Scale as a Reference System

The major scale is the foundation of the language of music theory. To visualize it, it helps to step away from the guitar briefly and consider the piano keyboard. That might sound strange in a guitar course, but the guitar makes some things harder to see: the same middle C can be played in five different places on the neck, while on a piano every note has one and only one location. You don’t need to learn piano; the keyboard just makes the underlying structure easier to see.

The piano organizes the twelve notes of the chromatic scale into repeating groups of seven white keys and five black keys. The five black keys are subdivided into groups of two and three:

The names of the notes are based on seven letters that range from A to G, which all fall on white keys:

The black keys are named relative to their neighboring white keys, and each one has two names. The black key just to the right of a white key adds a sharp (#) to the white key’s name. The black key to the left of a white key adds a flat (♭).

The small numbers inside the black note circles are scale degrees, which denote the position of each note inside the scale.

It turns out that if you start on a C note on the piano and construct a major scale, it falls entirely on white keys. This means that the key of C Major contains no sharps or flats, which makes the C major scale on a keyboard a great visual reference. The name has two parts: C is the root, and major means the other notes are related to C by that specific set of intervals.

Scale degrees and intervals are related but different ideas. Scale degrees are positions inside a scale, always counted from the root: in C major, C is 1, D is 2, and so on up to B at 7, and then C is 1 again. Intervals are distances measured in semitones, and you can measure them between any two notes. There are twelve possible interval distances ranging from 0 to 11 semitones, and the intervals take their names from the major scale.

Here’s how this chart was constructed:

• The major 2nd, 3rd, 6th, and 7th intervals (abbreviated M2, M3, M6, and M7) are each named after the corresponding scale degree of the major scale.
• The fourth and fifth scale degrees are called perfect intervals, so they are abbreviated P4 and P5.
• A minor interval is created by shrinking a major interval by one semitone. This gives us the minor 2nd, 3rd, 6th, and 7th, abbreviated m2, m3, m6, and m7.
• A perfect interval raised one semitone is called augmented. If flattened, it is called diminished. That accounts for the one remaining interval: the six-semitone interval between the 4th and the 5th, which is called either an augmented 4th or a diminished 5th. It’s also called a tritone, since six semitones is three whole steps.
• In practice, we can often drop the terms major, minor, perfect, augmented, and diminished. We can simply refer to each interval by the closest larger major scale interval, and add a flat symbol (♭) if it isn’t a major scale interval.

You don’t need to memorize all of those details. The point is that once you know the major scale, the interval names stop being an arbitrary list and become something you can work out. Scale degrees always refer back to the root, but intervals measure the distance between any two notes: from the 2nd scale degree up to the 4th, for example, is three semitones, a minor 3rd.

Note that, by default, intervals are measured moving up in pitch, so if we are measuring a downward interval, we have to explicitly say so. When talking about an interval going up, we usually say “of” rather than “above,” so we can say that F is the ♭3 of D, or D is the ♭3 below F. Measured upward from F instead, D is the major 6th of F. This can get confusing, so I’ll try to be clear about what I mean throughout the course; most of the time, an interval name means the distance going up.