Intervals
The distance between two notes
Play any note, then play another one higher up. The gap between them, how far apart they are, is called an interval. Small gap or big gap, every pair of notes has one.
Intervals are what make a melody rise and fall instead of sitting on one pitch. Some moves are tiny, right next door. Others are big leaps across the staff. Getting a feel for the size of a jump moves your reading forward fast.
Hum a low note, then a much higher one: that is a big interval. Now hum the low note again, then a note just barely above it: that is a tiny one.
An interval is the distance between two pitches, and measuring it is a skill you lean on constantly, whether you are reading a leap or checking two notes against the line you already know. Every pair of notes forms one, near neighbors or far apart.
An interval's name has two parts, a number and a quality. This class is about the number, the part that tells you how far and the part you read first. The quality, its flavor, gets a class of its own, Interval Quality, which comes after half steps and the major scale.
Distance between two pitches is the raw material of both melody and harmony. A melody is intervals walked one after another; a chord is intervals stacked and sounded together. Read distance fluently and you are reading what music is actually assembled from.
Of an interval's two names, the number is the skeleton and the quality is the modifier: the number counts how many letter-names the distance spans, and everything finer refines that count. Build the number first, because the rest hangs off it.
The distance between two notes
What do we call the distance between two notes?
Counting the number
To find an interval's number, count the letter names from the bottom note to the top. The one trick: count the note you start on as one.
Start on C and go up to E. Count them out, C is one, D is two, E is three, so C to E is a third. Try C up to G: C, D, E, F, G, a fifth.
Count on your fingers from C up to A: C, D, E, F, G, A. Six fingers, so that jump is a sixth.
To get the number, count every letter name from the lower note to the higher, both ends included. The count starts on the bottom note itself, and forgetting that is the classic slip. C to E is C(1), D(2), E(3), a third; C to G is a fifth.
The method works from any note, on any line or space: name the bottom, count up the alphabet to the top, and the total is the interval. Drill it on notes you already read and it gets as quick as naming a single pitch.
Here is the subtlety that makes interval numbers trustworthy: the number is a pure letter-name count, blind to sharps and flats. C to E and C to E-flat are both thirds, because both span three letter-names, C, D, E. A sharp or flat changes the quality and leaves the number untouched.
Counting letter names, not half steps, ties the number to letter-positions on the staff, so a third is always three letter-names, whatever accidentals sit on them. Kept on separate tracks from the start, number and quality stop interval reading from sliding into guesswork later.
Counting the number
Counting inclusively (C, D, E), what interval is C up to E?
Steps and skips on the staff
Once you can count intervals, you can also spot the small ones by eye. The two smallest have nicknames, a step and a skip.
A step is a second, the tiniest move: a note on a line to the space right beside it, no gap between. A skip is a third, hopping over one position: a line to the very next line, or a space to the very next space.
Look at two notes close together. If one sits on a line and the other in the space right next to it, that is a step. If one line or one space sits between them, that is a skip. Your eye learns to see it without counting.
The staff lets you read the smallest intervals by shape instead of counting them out. A second, the step, sets a line against its neighboring space, the two notes stacked tight together. A third, the skip, jumps line to next line or space to next space, one position passed over.
That gives you a fast visual read: neighboring positions make a second, one position skipped makes a third. Bigger intervals you still count, but seconds and thirds turn up so often that knowing their look on sight speeds up everything else.
The reason the small intervals read at a glance is a parity rule sitting in the staff. Every odd interval, unison, third, fifth, joins like positions, line to line or space to space; every even interval, second, fourth, sixth, joins a line to a space. So two notes both on lines are some odd interval before you have counted a thing.
This falls straight out of the letter names alternating line, space, line, space up the staff. For that same reason, a line and the space beside it span a second, the step, and neighboring lines span a third, the skip; both follow from the alternation and are not separate facts. That parity is what lets a practiced eye skip counting the small intervals entirely.
Steps and skips on the staff
Two notes a "step" apart, like a line and the space right beside it, form which interval?
The family up to the octave
Intervals have names all the way up. Two of the same note, no gap at all, is a unison. Then come the second, third, fourth, fifth, sixth, and seventh, each one letter wider than the last.
At the top of the group is the octave, the jump from one note to the next note that shares its name: C up to the next C, eight notes from bottom to top, both of them C. It sounds so alike that we give it the same letter, only higher.
Sing a note, then sing the "same" note way up high. That matching-but-higher note is an octave away.
The core intervals run in order: unison (the same note), second, third, fourth, fifth, sixth, seventh, octave. Each is one letter-name wider than the one before, so counting alone places any of them.
The octave is the one to know cold: eight notes, bottom and top sharing a name, C to C or G to G. Past it the intervals repeat an octave higher, a ninth being an octave plus a second, so unison through octave is the core working set.
The octave is the natural ceiling for an acoustic reason. Its two notes vibrate in a two-to-one ratio, a bond so close the ear fuses them into one pitch heard at two heights, which is why they share a letter in the first place.
Everything wider than an octave is bookkept as an octave plus a remainder: a tenth is an octave plus a third, and it behaves harmonically much like the third it contains. So the within-octave set is the real vocabulary, and the rest is that vocabulary counted again an octave higher.
The family up to the octave
The jump from one C up to the next C is which interval?
Melodic, harmonic, and a word on quality
An interval sounds two ways, depending on how you play it. Play the two notes one after the other and you hear a little melody, so we call it a melodic interval. Play them at the same time and you hear them blend, a taste of harmony, so we call it a harmonic interval.
The distance is the same either way. C up to G is a fifth whether you play C then G or both together. Only the texture changes, a line of sound or a stack of it.
Play two notes back to back, then press them together into one sound. It is a single interval both times, just introducing itself twice.
The same interval turns up two ways. Played in sequence it is a melodic interval, the material of tunes; played together it is a harmonic interval, the material of chords. You count the number the same way for both, so one reading skill covers a melody line and a chord alike.
This is also where an interval's second name waits. Two thirds can cover the same three letters and still sound different, one brighter, one darker, and that difference is the quality. Those two thirds are major and minor; perfect, another quality name, belongs to unisons, fourths, fifths, and octaves. Number now; Interval Quality measures major and minor thirds in half steps.
Quality is the layer this class holds back, and its mechanism is the semitone. A major third and a minor third both span three letter-names, C to E and C to E-flat, yet the minor sits one semitone narrower, and that single semitone is the distance between a bright chord and a darker one.
Sounded one after the other, an interval is melodic; sounded together, it is harmonic, and its number is counted the same way for both. Number fixes which letters the interval touches; quality fixes its exact width and the color riding on it. The number is the frame, and this is the class that builds the frame.
Melodic, harmonic, and a word on quality
An interval whose two notes are played one after another is called what?
Ready to play?
You can count the number of an interval now. Try the game on Easy, where every answer has a different number.