Rules for 4ths:
- The intervals that are white notes use only white piano keys. Those that are black notes use at least one black piano key.
- 4ths use four letters. (For example, C—F is C D E F.) Their “size” depends on how many keys we skip.
- A diminished 4th skips three keys. It is two whole steps.
- A Perfect 4th skips four keys. It is two whole steps + a half step.
- An augmented 4th skips five keys. It is three whole steps.
- An augmented 4th is frequently called a “tritone”. A diminished 5th also skips five keys, also is three whole steps, and also is called a “tritone”.
Note to more advanced students:
- Circle one shows a C aug chord resolving to an Ab chord.
- Circle two shows a F sus chord moving to an F7 chord, resolving to a Bb chord.
- Circle three shows C#dim7 chord resolving to an Em chord.
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