Wide intervals and the tritone
Count sixths, sevenths and the tritone quickly by working back from the octave, know how each tends to sound, and use a four-step checklist to name any interval.
SIX LETTERS
Sixths: 8 and 9 half steps
C to A covers six letters, C D E F G A, so it's a sixth. A major sixth is 9 half steps, C to A. A minor sixth is 8, C to A♭. Played together, both sound wide and sweet to most people; the major sixth usually comes across as warmer and brighter, the minor sixth as softer and a little bittersweet.
Sixths are thirds turned upside down. C up to A is 9; A up to the next C is 3, a minor third. 9 + 3 = 12.
Shortcut: count back from the octave.
C up to A
the next C is 12
B = 11
B♭ = 10
A = 9 -> major sixth
C up to A♭
one more step back = 8 -> minor sixthThree moves back from 12 instead of nine moves up from C.See how far the top note is from the octave, then subtract that from 12.
Check yourself
Nazanin plays E4 and then C5. She wants to name the leap. What is it?
- A major sixth, 9 half steps
- A minor sixth, 8 half steps
- A perfect fifth, 7 half steps
- A minor seventh, 10 half steps
Show the answer
A minor sixth, 8 half steps
Right. E to the next E would be 12; back to D♯ is 11, D is 10, C♯ is 9, C is 8. Six letters, E F G A B C, so a minor sixth.
The two sevenths: just short of the octave
Minor seventh · 10
C to B♭: a whole step short of the octave. Played together, most people hear a mild tension, restless but not harsh. It's the extra note that turns many chords into seventh chords, which you'll meet later in this course.
Major seventh · 11
C to B: only a half step short. Played together, it rubs like a half step stretched wide, and most people hear it as sharp and tense. One after the other, the B feels as if it wants to go up to C.
Check yourself
Count up from the first note. Sixth or seventh?
- C up to A
- C up to B♭
- G up to E
- D up to C
- C up to A♭
- F up to E
Show the answer
Sixth · 8 or 9: C up to A, G up to E, C up to A♭
Seventh · 10 or 11: C up to B♭, D up to C, F up to E
Tritone
An interval of 6 half steps, exactly half an octave: C to F♯. Because 6 + 6 = 12, a tritone flipped upside down is still a tritone. Most listeners hear it as unstable: it doesn't sound wrong so much as unfinished, as if it wants to move somewhere. On white keys alone, F to B is a tritone.
Play B with the F above it, then move B up a half step to C and F down a half step to E. The tension drains into C and E, a restful major third. That little move is called resolving.
Check yourself
Kimia plays C up to F♯, then F♯ up to the next C. Both jumps are tritones.
Show the answer
True
True. C to F♯ is 6 half steps, and F♯ to the next C is the other 6 that make up the octave. The tritone splits the octave exactly in half, so it's the one interval that flips into itself.
Checklist: name any interval
- Count the half steps
Start key is 0. If the top note is close to the octave, count back from 12 instead.
- Count the letters
Include both ends. This gives the number: third, fifth, sixth, seventh.
- Put number and count together
1 half step, 2 whole step, 3 and 4 thirds, 5 fourth, 6 tritone, 7 fifth, 8 and 9 sixths, 10 and 11 sevenths, 12 octave.
- Check it against the sound
If your count says fifth but what you heard was tense and restless, count again. The number and the sound should agree.
Sound check for the wide ones
- Sixths (8, 9): wide and sweet; the major one warmer, the minor one softer.
- Tritone (6): restless and unfinished, wants to move.
- Minor seventh (10): mild tension, a whole step short of home.
- Major seventh (11): sharp rub, almost an octave, pulls up to it.
Check yourself
Sara hums two notes. The second is so high it almost sounds like the first note again, yet it grates and she feels an urge to nudge it up a little more. What is she most likely humming?
- An octave, because it sounds like the same note
- A minor sixth
- A major seventh
- A perfect fifth
Show the answer
A major seventh
Yes. Almost an octave, a sharp rub, and a pull upward: that's the major seventh, 11 half steps, one half step short of home.
Check yourself
Count up from the first note and match each pair to its interval
Show the answer
- F up to B → Tritone (6)
- E up to C → Minor sixth (8)
- G up to E → Major sixth (9)
- D up to C → Minor seventh (10)
- F up to E → Major seventh (11)
Lesson recap
- Minor sixth = 8 (C to A♭), major sixth = 9 (C to A); both sound wide and sweet to most people.
- Minor seventh = 10 (C to B♭), major seventh = 11 (C to B), almost an octave and pulling up to it.
- The tritone is 6, exactly half an octave (C to F♯), and most people hear it as unstable.
- For wide intervals, count back from the octave: 12 minus what's missing.
- To name any interval: count half steps, count letters, then check the name against the sound.