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An interval of a Perfect 4^{th} is five
half steps above or below the starting note.
From A to D is an interval of a Perfect 4^{th}
** How to Find Perfect 4ths Above and Below any
Note.**
You remember how to find a
Perfect 5^{th} above or below a note. Just count two steps
forward (above) or backward (below) in the Cycle of Thirds. To find
Perfect 4^{ths} above or below a note just do the opposite.
A **Perfect
5**^{th} above is two steps **forward**, therefore a **
Perfect 4**^{th} above is two steps **backward**.
A **Perfect 5**^{th} below is two
steps **backward**, therefore a **Perfect 4**^{th} below
is two steps **forward**.
If you want to see the
structure behind why Perfect 4^{ths} are found in the
opposite direction as Perfect 5^{ths}, study the
illustration below.
**The Principle of Inversion**
When the same note name that is a Perfect 5^{th}
above a note is also a Perfect 4^{th} below the same note
(such as the E’s above and below A in the preceding illustration),
this is known as the principle of inversion. The interval of A up to
E becomes inverted when you keep the same A but refer to the E below
it (E up to A). Perfect 5ths invert to Perfect 4^{ths}. This
is why you count in the opposite direction of the Perfect 5^{th}
to find the Perfect 4^{th}. Because the cycle is in thirds,
the note that is a perfect 4th above will be two steps backward, not
forward. And a note that is a Perfect 4th below will be two steps
forward. For example, if you look at the image above, two steps
backward from A (counting in thirds) is F, then D. D is shown as a
P4 above A.
**Finding
Perfect 4**^{ths}
Focus on mastering finding Perfect 5^{ths
}first. Then just count in the opposite direction for 4^{ths}.
To find a Perfect 4^{th} above D, remember that a Perfect 5^{th}
above is two steps forward in the Cycle of Thirds, then just count
in the opposite direction (backward) two steps in the cycle to G. G
is a Perfect 4^{th} above D. A Perfect 4^{th} above
E is two steps backward to A.
To find a Perfect 4^{th}
below D, remember that a Perfect 5^{th} below is two steps
backward in the Cycle of Thirds, then count in the opposite
direction (forward) two steps. A is a Perfect 4^{th} below
D. A Perfect 4^{th} below E is two steps forward in the
Cycle of Thirds to B.
Remember that the **b**unny
(**B**) is looking up to the **f**ly (**F**), so when
moving from B to F you must raise F one half step to F#.
Also, the **f**ly (**F**) is looking down at the **b**unny
(**B**). This means that when moving from F to B you must lower B
by one half step to Bb.
**From B to
F** **From F to B**
Raise F 1/2 Step Lower B 1/2 Step
B#
to F##
F## to B#
B to F#
F# to B
Bb to F
F to Bb
Bbb to Fb
Fb to Bbb
Notice that when finding either Perfect 5^{ths} or
Perfect 4^{ths}, you must always raise F and lower B. It
works the same for both Perfect 5^{ ths} and Perfect 4^{
ths}.
**Summary
for Finding Perfect 4**^{ths}
First master finding Perfect
5^{ths} above or below a note. To find Perfect 4^{ths
}just count two steps in the opposite direction. Remember that
the signs match. If a Perfect 4^{th} below G is D, then a
perfect 4^{th} below G#
is D#
and so on.
**Exercise:**
Fill in the blanks with the
note that is a Perfect 4^{th} above the given note. Remember
to count two steps backward in the Cycle of Thirds. Also, remember F
to B (lower B one half step). Use the interval
Answer Charts to check your answers.
1. A
_________ |
2. Eb
_________ |
3. B
_________ |
4. F
_________ |
5. C#
_________ |
6. D
_________ |
7. Gb
_________ |
8. A#
_________ |
9. E
_________ |
10. Bb
_________ |
11. F#
_________ |
12. C
_________ |
13. G
_________ |
14. D#
_________ |
15. Ab
_________ |
16. E#
_________ |
17. B#
_________ |
18. Fb
_________ |
19. Cb
_________ |
20. G#
_________ |
**Exercise:**
Fill in the blanks with the
note that is a Perfect 4^{th} below the given note. Remember
to count two steps forwards in the Cycle of Thirds. Also, remember B
to F (raise F one half step). Use the interval
Answer Charts to check your answers.** **
1.
_________ A |
2.
_________ Eb |
3.
_________ B |
4.
_________ F |
5.
_________ C# |
6.
_________ D |
7.
_________ Gb |
8.
_________ A# |
9.
_________ E |
10.
_________ Bb |
11.
_________ F# |
12.
_________ C |
13.
_________ G |
14.
_________ D# |
15.
_________ Ab |
16.
_________ E# |
17.
_________ B# |
18.
_________ Fb |
19.
_________ Cb |
20.
_________ G# |
** **
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