by Roger Chartier:
we will transpose by intervals. The best part about this is that it is a simple trick and once you know how to do the trick it is easy! On your guitar, mandolin, banjo or any fretted instrument you can count the frets up or down. Same for the keys on your piano. These are basic intervals.
If you have a song that starts with a G chord and you want to be able to sing it higher you might choose to transpose it to the key of A. Here's how.
Consider the starting chord of the song as it is and looking at the chart you can see that the interval distance from
G to A is 2 half steps up. The distance from G to C is 5 semitones of half steps (up) as they are called.
This is simpler but different approach than transposing by scales. Same result.
So each chord in the song must change by the same amount.
The note C# is the same note or chord as Db, therefore, it's in the same box below.
Therefore, C# is Db and so it goes that
D# is the same tone or chord as Eb etc. you get the idea.
A (#note) or sharp note is one half step or one fret or one piano key higher. A (b note) or flat is one step lower. E to F, as well as B to C, have no flat or sharp between them.
Now as you change or transpose each chord remember that if it is a major or minor or diminished etc., It will still be thus.
|C||C# - Db||D||D# - Eb||E||F||F# - Gb||G||G# - Ab||A||A# Bb||B||C|
So by example you can see that a song with the chords
G - Em - C - D is relatively same as C - Am - F - G but in the key of C rather that the key of G
A- -D - E7 is relatively the same as G - C - D7 or C - F - G7 or E - A - B7 or F# - B - C#7
Have fun with this simple math trick and soon you will be able to do a transposition on the fly.