Intervals
Before we can talk about any music theory, it's important for us to know our intervals.
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Intervals are the distance between notes. Much like how we measure the distance between objects (meters, kilometers, miles, etc), the distance between notes is measured using intervals.
Table Of Contents:
Chromatic / Semi-tones / Whole-tones
If you were to look at the keys on a piano, it consists of white keys and black keys.
When these notes are played in order ascending (C, C#/Db, D, D#/Eb, etc.) or descending (C, B, A#/Bb, A, G#/Ab, etc.) they are referred to as a chromatic scale. A chromatic scale consists of only half-steps or semi-tones. Two half-steps make a whole-step or a whole-tone.
Intervals between neighboring white notes.
Notice that E and F as well as B and C are only a semi-tone apart, as they don't have a black key between them.
Minor 2nd / Major 2nd
Notes that are in a step wise sequence are called 2nds. Whole-steps are called major 2nds, and half-steps are referred to as minor 2nds.
Minor 3rd / Major 3rd
The next two intervals after the minor and major 2nds are the minor 3rd and the major 3rd, respectively.
Minor 3rds are 3 semi-tones apart, while major 3rds are 4 semitones apart.
Perfect 4th / Perfect 5th
After the 3rds, the next interval is called a perfect 4th, which is 5 semi-tones apart.
*We will leave the interval with 6 semi-tones for the end.
The interval with 7 semi-tones is called a perfect 5th.
Minor 6th / Major 6th
The perfect 5th is followed by the minor 6th which is 8 semi-tones apart, and the major 6th which is 9 semi-tones apart.
Minor 7th / Major 7th
The final two intervals before we reach the octave are the minor and major 7th.
Minor 7ths are 10 semi-tones apart and major 7ths are 11 semi-tones apart.
Perfect One / Perfect Octave
Two of the notes with the same pitch and the same register are unisons, or perfect ones (first). Two notes an octave apart are called perfect octaves or perfect eights.
Intervals Larger Than An Octave
There are more intervals beyond the octave, and their naming system is very similar to the intervals we have looked at so far. They have the same name as their previous octave, and their intervallic number is added by 7.
Octave + Minor 2nd = Minor 9th
Octave + Major 2nd = Major 9th
Octave + Minor 3rd = Minor 10th
Octave + Major 3rd = Major 10th
Octave + Perfect 4th = Perfect 11th
Octave + Aug 4th / Dim 5th / Tritone = Aug 11th / Dim 5th
Octave + Perfect 5th = Perfect 12th
Octave + Minor 6th = Minor 13th
Octave + Major 6th = Major 13th
Octave + Minor 7th = Minor 14th
Octave + Major 7th = Major 14th
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These intervals are obviously not as common as the ones within the octave, however, it is handy to know them as they are used to refer to larger intervals.
The Tritone
The tritone is the interval that is separated by 6 semi-tones.
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The technical term for the tritone is augmented 4th or diminished 5th, based on its enharmonic spelling of the interval. When the note names are a fourth apart it is called augmented 4th (D to G#), and when the letters are a fifth apart they are called diminished 5th (D to Ab).
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Even though G# and Ab are the same note, and an augmented 4th and a diminished 5th are the same interval, because of their theoretical difference they have different names and are considered different intervals. In some genres of music and groups of musicians the enharmonic names of notes matter greatly, however, among jazz musicians they do not matter. The interval separated by 6 semi-tones is simply referred to as a tritone.
Glossary
Intervals: The distance between notes.
Chromatic Scale: Series of consecutive notes that are semi-tones apart.
Semi-tone: Minor 2nd apart, half-step apart
Whole-tone: Major 2nd apart, full-step apart
Minor 2nd: Semi-tone, half-step apart
Major 2nd: Whole-tone, full-step apart, 2 semi-tones apart
Minor 3rd: 3 semi-tones apart
Major 3rd: 4 semi-tones apart
Perfect 4th: 5 semi-tones apart
Perfect 5th: 7 semi-tones apart
Minor 6th: 8 semi-tones apart
Major 6th: 9 semi-tones apart
Minor 7th: 10 semi-tones apart
Major 7th: 11 semi-tones apart
Unison: Pitches of the same note and same register.
Perfect One: Distance between two same notes in the same register.
Perfect Octave (Perfect 8th): Distance between two same notes one octave apart, 12 semi-tones apart
Tritone: Distance between notes 6 semi-tones apart
Enharmonics: Notes that share the same pitch, however, they have different names.
E.g. C# and Db