Which instruments do we have to think about when transposing a perfect 5th?
The most common instrument we think about when transposing a perfect 5th is the French horn! This is because when the French horn plays a C we actually hear a G.
But firstly…Why is the 5th called perfect?
Remember with the intervals of a 5th, 4th and octave we don’t use the descriptive words, ‘major’ or ‘minor’.
This is because these interval’s do not vary whether they are in the major or minor scales. This means that they only have one ‘normal’ state which is perfect!
Let’s have a look if we write out the C major scale below:
And then write out the C minor scale…
What do you notice about the 4th, 5th and 8th notes in both of these scales?
They are the same!
Let’s also look at the F scales… here is the F major scale:
Here is the F minor scale.
What do you notice? That’s right, the 4th 5th and 8th notes are the same!
Now back to the interval of a 5th….
Remember we said that we use the transposition of a perfect 5th when we think about the French horn. This is because when the French horn sees a C, we hear a G.
Let’s think about that…
We see a C
We hear a G
Let’s write out the C major scale… What is the 5th note?
That’s correct it’s G!
As you read earlier, the 5th only has one normal state and that is perfect, so we know that this is a perfect 5th already. So in order to write out the sounding pitch (the note we hear), we must transpose up a perfect 5th.
Now we are clear with that.. Here is a short melody in C major
We have already worked out that if we transpose a C up a perfect 5th we get a G. This means that we now need to put the key signature of G major at the start of our melody.
The key signature of G major has one sharp.
- If you are still unclear on your key signatures, please make sure you are familiar with your circle of fifths.
Once you have changed your key signature, we then need to follow this with transposing all the notes in the melody up a perfect 5th.
Let’s try another example
What key is our melody in below?
That’s correct, we are in A major!
Can you transpose up a perfect 5th from A?
The fifth note above A is E. This means we now need the key signature of E major. How many sharps does E major have? 4!
Once you have changed the key signature, simply move all of your notes up a 5th.
Notice that the interval of a 5th matches perfectly with our Circle of fifths!
Clue’s in the name….
What about accidentals?
This is very simple if you have seen the previous blog posts.
Remember when we are presented with an interval, we work out the descriptive word by asking ourselves, is the top note in the scale of the bottom note?
So if we have the below interval…
We can clearly see that this is a 5th … but how do we check that this is a perfect 5th?
We ask ourselves:
Is our top note in the scale of our bottom note?
Is D in G major?
The answer would be yes!
Let’s now add an accidental in:
Is Bb in Eb major?
It absolutely is, so this is a perfect 5th.
If we had been presented with a B natural then you would need to add in a flat sign in order to make it a perfect 5th.
You must always pay attention to your accidentals and treat these separately.
I hope that has given you a clear overview of how to transpose up a perfect fifth!
Check out my other blog posts here!