Hearing numbers in a key

Practice it: Hear the Number

Players talk about notes and chords by their number in a key: the 3rd, the ♭7, the IV chord. A number means the same thing in every key, so once you hear a 5 as a 5 you hear it in G, in E♭ and in a song you have never played. This primer is about hearing those numbers, which the Hear the Number game drills.

Setting the key

A number only means something once a key is set. A few chords set it: I, IV, V and back to I. The last chord sounds like home, and every other note is heard against it. In a minor key the chords are i, iv, V and i: the V stays major, so its 3rd leans up to the tonic. The short version is just V then I.

How each number leans

Listen for how a note feels over the key: some notes rest, and others lean toward a neighbor. That's quicker and surer than counting up from the tonic. Each button plays the cadence in C, then the note.

1 is home: it sounds finished.
2 sits a step above home, unsettled, falling to 1 or rising to 3.
3 is the major 3rd: the home chord's bright middle in major, a lift in minor.
4 leans down to 3, and wants to move.
5 is stable, the home chord's top, and can rest or fall to 1.
6 is warm and open, a step above 5.
7 is the leading tone: it pulls hard up a half step to 1.

The five notes outside the major scale sit between those seven. They sound like a turn away from the key, and each one wants to resolve to the scale note next to it.

♭2 crowds the tonic from a half step above and sinks to 1.
♭3 is the minor 3rd: the home chord's middle in minor, a dark turn in major.
♯4 is tense, a half step under 5, and pulls up to it.
♭6 is dark and sinks a half step to 5.
♭7 is the bluesy 7th: it falls to 6 and doesn't pull home.

In a minor key the scale's own 3rd, 6th and 7th are a semitone lower: 1 2 ♭3 4 5 ♭6 ♭7. The numbers keep their names, so the minor 3rd is ♭3 in either key.

Chords by number

Build a chord on each note of the scale and you get the key's seven chords. Upper case numerals are major chords and lower case minor; ° marks the diminished chord on 7. I, IV and V are the three major chords, and most songs lean on them. Each button plays the cadence, then the chord.

Major, minor, diminished, augmented

A chord's quality can be heard on its own, with no key. Major sounds bright and settled. Minor is darker. Diminished is tense and small, two minor 3rds stacked. Augmented is two major 3rds: it floats and doesn't settle.

Seventh chords and inversions

Add a 7th on top of a triad and the color changes again. The dominant 7 is a major chord with a ♭7: bluesy, and it wants to move on. Major 7 is soft and dreamy, minor 7 mellow. Half-diminished is a diminished triad with a ♭7, and diminished 7 stacks minor 3rds all the way up, so it sounds the same from any of its notes.

An inversion puts a note other than the root in the bass. The quality stays the same, but the chord sounds less settled, so it's harder to name. The game's More options add inversions, and can play each chord as a guitar shape from Chord Shapes in place of a close piano voicing.

Progressions

A progression is a few chords in a row. The game plays the cadence, then two to four chords starting on I, and you fill in the rest. Listen to where each chord goes from the one before: IV lifts, V pulls back home, vi is the minor chord next door. Each button plays the cadence in C, then the progression.

How to practice

Start the Hear the Number game's path at its first exercise, 1 and 5 in C, F and G, and add numbers as each set gets quick. The key and the octave change from question to question, so you hear each number by its place in the key. Answer on the pad or with the number keys: 1 to 7 pick the scale's own numbers. Play it asks you to play the note on your guitar, in any octave, which ties what you hear to the neck. Once the major scale is easy in those keys, the path moves it to every key, then to chords, minor keys, and the notes outside the scale.