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Interval
inversion
Interval inversion
refers to turning the interval upside down. The top note becomes
the bottom note, and the bottom note becomes the top note. Inversion
is accomplished by moving the bottom note up one octave or moving
the top note down one octave.

Notice that the number size
of an interval plus the number size of its inversion always adds
up to 9:
A 2nd inverts
to a
7th.
A 3rd
inverts to a 6th.
A 4th
inverts to a 5th.
A 5th
inverts to a 4th.
A 6th
inverts to a 3rd.
A 7th
inverts to a 2nd.
When an interval is inverted, its quality
usually changes as well as its number size. The only exception are
perfect intervals.
An augmented
interval when inverted becomes diminished.
A major
interval when inverted becomes minor.
A perfect
interval when inverted remains perfect.
A minor
interval when inverted becomes major.
A diminished
interval when inverted becomes augmented.


(Just a note about notation. Accidentals
should always be on the same line or space as the note it is affecting.
Notice the example above of the A2. The sharp is on the same
line as the F, and the flat is on the same space as the E. This
correct notation is the only way a reader would be able to tell
which accidental goes with which note. Make sure you observe this
rule both when reading music as well as when writing music.)
Considering the information above, complete the following:




Using interval inversions can be helpful in determining larger
intervals if the number of half steps for the smaller intervals
is memorized:
m2 = 1 half step
M2 = 2 half steps (or 1 whole step)
m3 = 3 half steps (or 1 1/2 steps)
M3 = 4 half steps (or 2 whole steps)
For example, what is a M7 above G?
The inversion of a M7 is a m2 (half step).
A m2 (half step) below G is F#; therefore, a M7 above
G is also F#.
Try this one on your own:

  
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