In this lesson we will learn how to move a tune up or down by the interval of a perfect 4th or perfect 5th. This is the interval of transposition needed when writing music for the French horn or cor Anglais. We will move the melody into a completely different key, and this means we also need to transpose the key signature.
Here’s a simple example. This tune is in C major.
To transpose the melody up by a perfect 5th, we first need to work out what the new key is going to be. The note which is a perfect higher than C is G, so our transposition will be in the key of G major, and we need to put in a key signature with one sharp, F#.
Now we take the first note of the tune, which is E, and move it up by a 5th, to B. The next note is C, so we write a G, and so on. You can either work out each transposition in turn, or you can instead look at the interval the melody moves by, and just copy that instead. Both methods should give you the same answer.
Here’s a tune in the bass clef, which we will transpose down by a 4th. It’s in D major, so we need to count down 4 notes from D, in the D major scale, to find the new key.
The new key will be A major, which has 3 sharps.
The starting note in the original is A, so count down 4 notes from A to find the new starting note, A-G-F-E, so the first note needs to be E. Carry on in the same way, either working out each note a 4th lower, or by moving along the melody with the same intervals.
