Intervals · Step 6
The distance between two notes
An interval is the distance between two notes, counted in semitones. C to D is two semitones; C to E is four. The count is what gives an interval its name, and the name is what lets you talk about a tune without saying which notes it uses: “up a third” means the same shape in any key.
The interval that matters most for everything that follows is the third, and it comes in two sizes. Four semitones is a major third, three is a minor third. The whole difference between a major chord and a minor one lives in that single semitone.
The drill plays two notes, one after the other, going up. Say whether the gap was a major or a minor third. Guess freely at first: the point is to start hearing the difference before you can explain it.