Intervals: The Distance Between Two Notes, Named Plainly

Strip everything else away and music hands you this: two notes, and the space between them. Play any note, then another, and you have made an interval. It has a size, counted in letter names (C up to E is a third, because C, D, E is three letters), and a quality (major, minor, perfect) that pins down the exact count of semitones. You do not need the whole naming system today. You need the idea underneath it: every distance has its own temperament, and your ear already knows them all.

One distinction helps before the tour begins. Play the two notes one after the other and you have a melodic interval, the step a tune takes. Play them together and you have a harmonic interval, the beginning of a chord. Same distance, two behaviours: a sixth sung in sequence is a leap with some yearning in it; the same sixth sounded together is a warm place to stand. Your ear treats the two differently, and the practice below works on both.

Restful and restless

Long before anyone taught you a term, your ear sorted the distances into two piles. Some sit still: the octave (the same note, higher), the fifth (open and sturdy, the sound of an orchestra settling to tune), the fourth. Some are warm without being finished: thirds and sixths, the distances harmony is mostly upholstered in. And some lean: the second, crowding its neighbour; the seventh, reaching for the note above it; and the tritone, the one distance in the octave that will not settle anywhere, which music has spent several centuries alternately avoiding and enjoying.

None of this needs believing on my say-so. Have a listen: play a low C, hold it, and walk a second note up from C sharp to the octave, one semitone at a time, letting each pair ring. Somewhere in you, each distance lands as a different weather. The names are only labels on jars your ear filled years ago.

Your ear sorted the distances into restful and restless long before anyone told you their names.

The two worth learning first

If the family feels large, start with two members. The third decides bright or dark: I wrote about that one note at length already, and it remains the best value in music. The fifth is the frame: so stable that when you place a third inside it you have built the ordinary chord, which is most of the furniture in most of the songs you know. Learn to hear a third and a fifth from any starting note and you have the load-bearing part of what intervals offer a songwriter. The rest is refinement, and it can arrive at its own pace.

How to practise the hearing

Counting is the entry; singing is the proof. Pick a note on the guitar (or in the chord builder, which will sound any two notes together patiently and without judging your intonation), play it, and sing the note a fifth above before you play that one to check. Then thirds. Then fourths. Five minutes most days is worth more than an hour once a month, in the way of most quiet skills.

I do some of mine on the walk round Waterloo Lake, which this week was all pedaloes and school holidays, humming a fifth against whatever note the world offers: a mower, a ringtone, the ice cream van. The world supplies more drones than you would think, and none of them minds being practised against.

Two notes, one distance, one temperament. Everything else I could tell you about harmony is an arrangement of this. Play the pairs and listen.