Music theory

Welcome to a guide to music theory divided in several parts. You will learn about notes, tones, pitches, intervals, chords, scales and several other subject that will develop your knowledge from a theoretical standpoint.

Notes, tones and pitches

The words note, tone and pitches can be confusing. Not at least notes and tones tends to be intermixed as synonyms but there are distinctions. It can be reasonable to treat them as synonyms in some cases, but in precise music vocabulary they can be separated.

A tone can be seen as a sound made by an instrument whereas a note is a description of a tone. A music sheet, for instance, notes are used to give information about the duration of a tone (quarter notes etc.).
We normally don’t say “the tones in a chord”, we say the “notes in a chord”. But we could say: “I like the tones coming from your piano when you playing that chord”.

A pitch, finally, refers to a frequency, measure in Hertz (Hz). The “Middle C”, for instance, which is the fourth C key on a full-size piano keyboard, have a pitch with a frequency of 261.6 Hz.

To plunge to deeper into the subject, a recommended lesson is Pitches and octave designations.

Intervals

Intervals are distances between two notes. The units for intervals are semi-steps and whole steps. There is one semi-step between C and C# and there is one whole step between C and D.

Intervals of two notes have different sound qualities. The sound character of notes with only one semi-step in between is dissonant (they lacks harmony) because they almost collide. Play C and C# together on a guitar or a piano and you will hear a quite unpleasant sound.

Notes with five scale steps between can sound rather firm (this interval constitutes the 5th chord, or the power chord). Thirds on the other hand is very often used in acoustic fingerpicking songs and in classical music played on a classical guitar. They have a very pleasing sound.

Some interval categories exist in different forms. There are, for instance, minor third and major third. These have the same intervals considering scale steps, but differ considering semi-steps. Besides the usual intervals, there are compound intervals, meaning an interval added to an octave.

Chords

Chords are among the most fundamental for musicians and often the first a beginner learn about. Chords are especially essential when it comes to guitar, but chords are also fundamental on other instruments, such as the piano. Chords, are however, not relevant for percussion instrument and only of minor importance for instruments like bass guitar or harmonica.

So that is a chord? Chords contains a set of tones, it can be three, four, five or even more. The most common chords contain three notes and are called triads. The most important triads are the major and minor chords.

We will not discuss chords any further, since there exist a dedicated article about chord theory on this site pointed to that subject.

Scales

Next to chords, scales are probably the most important concept for many instruments, including guitar and piano. Similar to chords, scales are groups of notes, but the difference is that you never play all the notes in scale simultaneously. A scale is like a palette of notes which a musician can put together in melodies, solos, licks and phrases.

Scales can guide you to relevant notes to use in a certain key to create a melody, or which notes to stick to then jamming over some backing instrument.

Types of scales

As with chords, there are different categories of scales. And there is also a hierarchy considering the importance. The most fundamental scales are the major and minor scales. Both these include seven notes and are called heptatonic scales (a theoretic term that isn’t necessary to learn).

As with chords, scales have root notes. In the C major scale C is the root note, in the A minor scale A is the root note. You get it by know.

Major and minor, and the key relationship

One reason to why these scales are the most important is that the major and minor scales is identical with keys in music. So, what is a key, you may ask? Perhaps you have stumble into titles of classic music – Franz Shubert’s Sonata in C minor or Wolfgang Amadeus Mozart’s Violin Concert No. 3 in G major? The titles explain that the actual pieces are composed in these particular keys; a common routine in classical music, not equivalent in pop or jazz.

If you are interested there are statistics of which keys that have been used in most music compositions. As told by the source is keys with none (C major) and few accidentals (such as F, D and G major) most common.

When someone refer to D major, the same thing could be referred to the key of D.
D major scale: D E F# G A B C#
The key of key: D E F# G A B C#

Sometimes it's good to be pronounced when explaining things that could be new knowledge.

But it's vital to know some underlying distinctions. When it's referred to D major it's refereed to exactly these notes: D E F# G A B C#. But it's not sure that a musical piece that goes in D major exclusively is limited to these notes. Music doesn’t follow strict formulas.

The second main purpose by learn major and minor scales is that you thereafter know which notes are included when someone says: this tune goes in the key of …

Scale degrees

Another way to organize scales is by degrees. Degrees explains the relationship of the notes in a scale. They have names and also Roman numerals.

Tonic (I): The first note of a scale.
Super tonic (II): The second scale degree.
Mediant (III): The third scale degree.
Subdominant (IV): The fourth scale degree.
Dominant (V): The fifth scale degree.
Submediant (VI): The sixth scale degree.
Subtonic (VII): The seventh scale degree.

If it's referred to the dominant chord, it's the chord which root note which also is the fifth scale step. In the key of C major, G is the dominant. When a scale is harmonized into four-note chords, the dominant will be a seventh chord, which also is known as the dominant chord. In the key of C major, G7 is the dominant four-note chord.

Stability and resolution

In the major scale, the degrees are written as 1, 2, 3, 4, 5, 7. This makes it clear the major scale is the most fundamental of scales. What is interesting is that some of the notes in the scale can be said to be stable and some unstable.

The 7th is the most instable. This is the subtonic, also called the leading tone, which is telling since it often leads back to the tonic, the 1st. Being an instable tone means that it sounds as the music wants to go on much more than stay. You can experiment by playing around in the C major and notice how the B note is less stable when for example the A tone and how B "wants" to resolve to C.

The second unstable tone in the major scale is the 4th. It wants go up to the 5th or down to the 3rd. You can experiment in C major and this time hear how the F tone is unstable and how natural it is to continue to G or A.

This is not only true for notes by also for chords. And this is why the V chord is unstable and wants to resolve back to the I chord. The V chord can be even more unstable when it's become a 7th dominant (V7). For example, in C major, G7 is the 7th dominant chord - notice how it includes both the B and F notes. A typical progression is F - G7 - C, in which C is the "home" chord that G7 resolve to.