Intervals? What’s an interval? Good question. Have you ever played on the stairs? My kids did – even when they weren’t supposed to. You know, how many stairs can you skip on the way down? How stairs can you jump on the way down? How many stairs can you skip on the way up? Think about that for a minute. That’s going to help you learn about intervals.
What is an interval?
An interval is a way of measuring the distance in pitch from one note to another. Intervals help us figure out if we must hop to a note, skip to a note, or jump to the next note. Kind of like playing on the stairs. Do you just step up to the next stair, skip a stair, or jump down the last 4 stairs.
Why should I learn intervals? What’s in it for me?
Learning to read music by intervals will help you be better at sight reading. (Reading music without practicing it lots of times first.) Reading intervals also helps you transpose music in your head better and faster. If you are a non-piano player, learning about intervals and how they sound will help you hear if you are playing the right note. (Or, if you are playing in tune!)
Recognizing Intervals
Because we are talking about distance, intervals are named with numbers. The numbers represent how many notes (or steps) are included in the interval. Bottom note + top note + notes in between = interval. We write intervals with the notes one after the other or with the notes “stacked” on top of each other. Like part of a chord. Intervals can go up from a note, or down from a note.
Interval of a 2nd
2nds are notes that are one step apart. You might say they are next-door-neighbor notes. Or like going from one step on the stairs to the next one. When we write them on the lines and spaces of a staff one note will be on a line, and the other note will be on a space, either higher or lower than the first note. Here are examples of how 2nds look when they are written on a staff, and when they are played on a keyboard.
Interval of a 3rd
3rds are a little further apart than 2nds. 3rds skip over a note. Like standing on the bottom step, skipping over the next one, and going to the 3rd step. When we write 3rds on a staff either both notes are on lines, or both notes are on spaces. We go from line to the very next line, or from space to the very next space. On a keyboard, one note sits in between the top and bottom notes of a 3rd.
Interval of a 4th
Guess what! 4ths are just a bit further apart than 3rds. Like going up stairs and trying to skip over two steps. Or jumping down the stairs over the last two steps. If one note of a 4th is on a line, the other note is on a space. If you look at a 4th on a keyboard you will see that two empty notes are between the bottom not and the top note.
Interval of a 5th
By the time we look at a 5th we are jumping from one note to the next. I do not recommend trying 5ths on the stairs! 5ths are intervals whose notes are either both line notes or both space notes. Either the notes go from line to line with an empty line in between or from space to space with an empty space in between. Take all the fingers of one hand and place them on consecutive notes on a keyboard. Then play the note under your thumb, and the note under your little finger, and you have played a 5th. Now, if you play the 3rd finger, you just played a 3rd from the bottom of the 5th, and a 3rd from the top of the 5th. Very convenient to play – 5ths fit right under your fingers.
Interval of a 6th
On to a bigger jump! Definitely do NOT do this on your stairs!! 6ths are more line-space intervals. If one note is on a line, the other note must be on a space – with two empty lines and two empty spaces between the top and bottom notes. Remember how you put your hands on the keyboard for a 5th? Do the same thing, except make your last finger stretch out to one extra note. You just played a 6th. 
Interval of a 7th
7ths are really big jumps! A 7th is another interval that goes from line note to line note, or space note to space note. Line to line with 2 empty line between or space to space with 2 empty spaces between.
Octaves
Octaves are intervals of an 8th. They get their own special name. Octaves are special, because both the top note and the bottom note have the same letter names. From A to A makes an octave. Or from F to F. Or from D# to D#. We write one note on a line and the other on a space. The two notes sound the same – one is just higher than the other one. 
So, learn your intervals! And make your musical life easier!