The word INTERVAL in music means:
The distance between two notes
This is great stuff to learn if you want to understand harmony and scales. Welcome to a thorough primer in all of the intervals that we frequently encounter in music.
The smallest interval in Western music is called a “half-step” or a “semi-tone”. A half-step is the distance between any key on the piano, and its adjacent key.
As I mentioned in my post called Relative Minor and Relative Minor the C major scale is derived from playing from C to C on the white keys. If we call the note C that we start on #1, then there are 7 white keys before we arrive back at C. So the major scale is a 7-note scale.
There are also 5 black keys between C and C. So there are a total of 12 half-steps in an octave. (7 white keys, 5 black keys, and 7 + 5 = 12)
Let’s start by learning the names of the intervals of the major scale.
1 - the first note of the scale, in relation to itself is called Unison, or technically, Perfect Unison.
2 - the second note of the scale is called a Major Second.
3 - the third note of the scale is called a Major Third.
4 - the fourth note is called a Perfect Fourth.
5 - the fifth note is called a Perfect Fifth.
6 - the sixth note is called a Major Sixth.
7 - the seventh note is called a Major Seventh.
8 - then we arrive back at another C an octave up, so we call this an Octave, or technically a Perfect Octave.
Why in the heck are some notes called “major” and some called “perfect”?
(It doesn’t really matter, so if you don’t care, skip down to where it says “the formula for figuring out the names of the intervals.”)
If you really want know, the “perfect” intervals are the most consonant (least tension created, most sense of stability and rest.)
Sound is vibration, and the most consonant notes vibrate at simple ratios.
Perfect Unison is obviously two notes vibrating at the same frequency. Perfect Octave the top note is vibrating exactly twice as fast as bottom note. Perfect 5th, is a 3:2 ratio, and Perfect 4 is a 3:4 ratio.
None of this matters in practice, this is just the “why” behind the names.
ALL the other notes, have less “perfect” and more mathematically complex ratios and so create a lot more color, create more tension, are more dissonant.
Here is the formula for figuring out all of the names of the remaining intervals:
A MAJOR interval LOWERED by a half-step, is called MINOR.
And of course, conversely, a MINOR interval RAISED by a half-step, is called MAJOR
Both PERFECT and MINOR intervals, when they are LOWERED by a half-step, are called DIMINISHED.
Both PERFECT and MAJOR intervals, when they are RAISED by a half-step are called AUGMENTED.
Here is a list of all the intervals, and how many half-steps are in each interval:
Unison: 0 half-steps
Minor 2nd: 1 half-step
Major 2nd: 2 half-steps
Minor 3rd: 3 half-steps
Major 3rd: 4 half-steps
Perfect 4th: 5 half-steps
Augmented 4th / Diminished 5th / Tritone: 6 half-steps
Perfect 5th: 7 half-steps
Minor 6th: 8 half-steps
Major 6th: 9 half-steps
Minor 7th: 10 half-steps
Major 7th: 11 half-steps
Perfect Octave: 12 half-steps
Note that the middle interval, 6 half-steps, which is also one of the most dissonant intervals, has three names: augmented 4th, diminished 5th, or tritone. People will also commonly call it “a flat five” notated b5.
And I think that is a way more than you ever wanted to know in an introduction to the subject of intervals. HA! I told you I’m a nerd for this stuff… LMK what questions you have!