Transposing song that contains notes/chords outside the root key to a new key

Question

I've been trying to figure out how to change the key of a song. I have a chart like this:

_{(source: howmusicworks.org)}

I originally thought that I could just find the notes, and read off a different row, but apparently with the song I'm trying to change the key of, it doesn't work. The notes continually move out of that key.

For instance, the first few chords are in the key of E, but then the next chord is not in that key. But, straight after that chord, it returns back to the key.

How would I go about key changing this song?

Example chords:

Chord 1: D# Seventh Augmented Ninth Diminished Fifth

Chord 2: G# Chord

Chord 3: F Chord

Answer 1

The idea between changing keys is to move all of the chords the exact same distance. This will work for chords in the key and chords outside of the key as well.

When moving a chord to the new key the only thing that changes is the root note, the chord extension stays the same. For example, your first chord "D# Seventh Augmented Ninth Diminished Fifth" (or "D#7b5#9" is a shorter way to write it) the only part that changes is the root note "D#" and the "7b5#9" will stay the same. So for the purpose of moving to another key it might be easiest to work with just the root notes and then add the extensions back on once the new root notes are determined.

The root notes for the three chords you gave are:

  D#
  G#
  F

So lets say you want to move the D# to an F# (as an example). You first figure out how many steps you have to move to get from D# to F#.

 D# E F F#
 1  2 3 4

Then apply that exact same number of steps to all of the other chords in your song.

 G# A A# B
 1  2 3  4

 F F# G G#
 1 2  3 4

So your final chords are:

 F#7b5#9
 B
 G#

This approach works for any chord in the song, whether it is a chord in the key or an outside chord. As long as they all move the same distance then the relationship between the chords stays the same.

Answer 2

Okay - so if I understand your question correctly you are attempting to use your chart to transpose a song from one key to another. But the problem arises whenever the song you are transposing contains chords that are outside the root key - so the chart does not line up.

So here is what you do. Use your chart to find the chords based on the root note indicated in your chart by reading from the appropriate row as you indicated. When you get to a chord based on a note that is outside the key (non-diatonic), you need to determine the intervallic relationship between the preceding chords root and the chromatic (outside the key) chords root. In other words, how many semitones (half steps) separate the two root notes.

To easily figure out the answer - use the chart below and simply count the number of steps from one note to the other. Then count the same number of semitones from the note in the new key to find the next root note for the corresponding chord in the new key.

So using this method with your example - let's say you are transposing from your song in the key of E to the key of F. Your first chord is a D# Seventh Augmented Ninth Diminished Fifth. The root note of this chord is D# and is in the key of E so to transpose to the key of F you look at your chart and see that D# is 7th scale degree of the key of E so you go down to the 7th scale degree of your new key F and see that you will need a E Seventh Augmented Ninth Diminished Fifth. Next is the G# chord. From your chart we see that G# is the 3rd scale degree of E so for the key of F we will look at the 3rd scale degree and find an A chord.

But as you have discovered - when we get to the next chord (F) which is outside of the key of E - we can't find the F in the line for notes for the key of E so what do we do? This is where the new chart comes into play.

We look at the chart above and find the G# and count the number of half steps (semitones) between G# and F and we see that there are 9 semitones if we go higher (you must loop back to the beginning when you get to the B and go B to C - just like on a piano keyboard). If you take the new key of F and start with the note that preceeded the chromatic chord root which was A (see above) - and count 9 semitones from A on the chart above we land on Gb (also known as F#). So the chord we need in our transposition from E to F is Gb. Alternatively we can go in descending steps down from the G# to the F and see that there are 3 half steps or semitones between G# and F. So we can start on A and count 3 half steps to the left and again we land on Gb/F# - so it works in either direction.

EVEN EASIER - You will also note that the out of key chord root in our example amounts to a "flatted" second degree of the scale. So instead of the F# we have F which is the 2nd degree flatted. If we go to the new key of F and look at the 2nd degree of the F scale on your chart we find G. If we flat the G by one semitone we have Gb.

You can use the chart above to discover this as well. For the example in your question - simply take the 2nd scale degree of whatever key you want to transpose to and count one half step/semitone down and that gives you the equivalent flatted second degree for the new key. Use the corresponding root for the equivalent chord (be it major, minor, 7th, diminished, etc.) and you have the appropriate chord in your new key. This will work for any key you choose to transpose to.

Good luck.

Answer 3

There are two issues here: one is the execution of the transposed part, one is the notation. The answers I see here so far focus on the execution. Namely they suggest just moving everything up/down by the same number of semitones. Which is correct but only semi the story.

Notationally, you also need to maintain the scale difference. So if the noteheads are three steps apart before transposition, they need to be three steps apart after transposition as well. So basically the idea is to first transpose "graphically", namely shift all noteheads by the same distance as the tonics of the key change and afterwards adjust all semitones so that the actually executed pitch is correct again.

Of course, there are limits. If your original score contains some double sharps and you transpose from a key of c to c sharp, those double sharps would turn into triple sharps (for which there is no symbol). So either you need to transpose to d flat instead of c sharp, or you'll have to "break the pattern" and take evasive action for pitches that would become unprintable, namely effectively transpose to a tonic of d flat instead of c sharp just for those pitches.

So basically the idea is that if you transpose from C anything (sharp/flat/natural) to G anything else, then a D whatever will transpose into an A whatever else. So transposing from C sharp major to G flat major will transpose D natural into A double flat (C to G is a fifth in "graphical" distance, and the semitones match when you flatten A twice). It will also transpose B natural into F flat (graphical distance of B to F is five steps, but one semitone of the required distance happens to be already accounted for).