There are two main reasons for changing the key of a song.
1. Singing.
We each have our own vocal range, so if we want to sing a song, we need to make sure that the key for that song is suitable for our voice. That means we need to make sure that the song's highest and lowest notes are within our vocal range and we can sing them comfortably, otherwise we'll produce sounds of the type often heard in every karaoke bar in the world.
As guitarists, one very simple way to solve this problem is by attaching a capo, which automatically and effortlessly changes the pitch, and so changes the key. With no capo we have to change the chords according to the method shown below.
2. Difficult or unsuitable chords
This problem can't be solved by a capo. In this case, the key that the song is in has a particularly nasty set of chords. Those chords might be too difficult for your present level, or they might be unsuitable for the sound you require, such as if the song needs a lot of open strings to ring out, or extra notes to be added on here and there as decorations. Some keys require all barre chords, which, even if you can play them, won't leave you any open strings and won't leave you any free fingers to add on decorative notes either. It's not for nothing that they are sometimes called the unfriendly keys (at least for guitarists).
The keys that are considered most 'chord friendly' for guitarists are the major keys:
C, A, G, E &
D and minor keys:
Am Dm &
Em. Sometimes we find a song in an unfriendly key because it has originally been written for another instrument such as piano. Keys that are difficult or awkward for guitarists might be no problem for other instruments. The converse may also be true.
Example and method
Let's say we find the chords of a song are written in the very unfriendly key of
A flat major (Ab) as:
||Ab - - - Db - - - Eb7 - - - Ab - - - ||
etc.
Musically, that's a very simple three-chord song, but you might not feel that way after playing those chords, which are all barre chords - and you can forget about adding on any fancy extra notes, unless you've got an extra finger somewhere. Sometimes, we
do want all barre chords, and in that case that's exactly how the song should be played, but in this lesson we're assuming that you want chords with open strings that leave you some free fingers, either because barre chords are too difficult at your present level or because this particular song sounds better with open strings.
Transposing UP a semitone
Fortunately, we can easily transpose it by moving every chord either up or down by equal amounts.
First, we'll try moving
up a semitone, or
half step, to the
key of
A major. That's very simple in this case, because we just need to drop the
flat (b) from every chord, which gives us:
||A - - - D - - - E7 - - - A - - - ||
etc.
The song will sound the same but just a little higher in pitch, and will be far easier to play. Notice we DON'T change the chord type. The
seventh chord (
Eb7) remains a
seventh chord in the new key
(E7).
Transposing DOWN a semitone
Now, let's try moving down a semitone, or
half step.
Ab,
moves down to G
Db moves down to C
Eb7 moves down to D7
So now we have the same song in the
key of G major:
||G - - - C - - - D7 - - - G - - - ||
etc.
Again, it will sound the same but just a little lower and it will also be much easier than it was in the key of
Ab major. Will it be easier than
A? That's up to you. You can change it to whichever one you prefer. Sometimes, unfortunately, the original key may also contain an easy chord which might become a difficult chord when transposed to the new key. So your first choice of new key, may not always be the best one and you'll have to decide the best option based on your own ability and requirements. Such musical decisions are, of course, an essential part of being a musician.
So, as we've seen, transposing up or down by a semitone, or
half step is very simple. Doing so made the chords much easier and gave us a lot of freedom to add on extra notes with our freed up fingers, if we want. The pitch only changed a little, so if we could sing the song in the original key of
Ab, we can very probably sing it in either of those new keys of
A or
G.
Transposing a greater distance.
But what if we couldn't sing it in
Ab and we don't have a capo? We probably won't be able to sing it in
A or
G either, as they are very close in pitch. In that case we have to move it by a much bigger amount - as much as we need so that it fits our voice. So let's try transposing it to the key of
D major.
First we'll look again at the original key of
Ab major:
||Ab - - - Db - - - Eb7 - - - Ab - - - ||
etc.
The first chord in the original key is Ab
We know the first chord must be
D, because we're changing from
Ab to
D but how will we find the others? Well, the surest way is to count how many semitones, or half steps, we moved it when we transposed from
Ab to
D. Remember that some notes we pass through can have 2 names, such as
A# which is also called
Bb - so we can show that like this:
A#/Bb.
Ab - A - A#/Bb - B - C - C#/Db - D - That's SIX semitones. That means if we do exactly the same for the other chords, we'll always arrive at the correct chord in the new key.
The second chord in the original key is Db
So, as with the second chord, we have to move it up by SIX semitones, as follows:
Db - D - D#/Eb - E - F - F#/Gb - G
So our second chord in the new key is
G
The third chord in the original key is Eb7
Again we must move it up by six semitones:
Eb - E - F - F#/Gb - G - G#/Ab - A:
So our third chord is
A - and don't forget it must also be a
seventh chord, just like the original, so it's
A7
The fourth chord in the original key is Ab, So, of course, it must be
D again in our new key.
Our complete 'mini' song in the key of
D is:
||D - - - G - - - A7 - - - D - - - ||
etc.
A shortcut
Sometimes when transposing, we can spot some shortcuts. For example, in our mini song we had to shift the note up six semitones every time, which is quite a chore. But look at chords
2 &
3 in the original key.
Db and
Eb7. Those are very close neighbours. They are only
2 semitones, or
half steps apart. That means the new chords will be only
2 semitones apart in the new key too, and as you can see, the new chords are
D &
E7, which, as we predicted, are exactly
2 semitones apart.
So keep a look out for chords that are close neighbours - it saves us from having to count up lots of semitones.
Another shortcut that we can apply sometimes, if we know all the major scales, is to see the chords in terms of the degrees of the scale. In our mini song above, the chords are based on the
1st,
4th &
5th scale degrees. And they will always be those same degrees in every key. That in itself is a good reason to memorise all the scales, a feat which isn't nearly as hard as it sounds.
