1.18The tritone: the sound of instability

Play:

B + F

That's exactly the outer notes in:

B-D-F = B°

B-F is six semitones.

That interval is called a tritone.

Now play:

B + F

and resolve to:

C + E

Listen carefully:

B rises:

B → C

F falls:

F → E

This tiny movement is one of the most important sounds in Western harmony.

Now add G underneath the first pair:

G-B-D-F

That's:

G7

Then resolve to:

C-E-G

You have just heard:

V7 → I

This relationship will drive huge portions of our course.