Strategies for transposing in real time

I recently went to a ukulele meet-up to play some music and meet some people and I bought the song book that they use. It consists of mostly pop/rock songs and old folk tunes however, they have all been transposed to keys that are easy to play on the uke (C, F, G, D and, A). I am interested in now playing the songs along with the original records (just strumming the chords at this point) so will need to transpose them. As an exercise I’d like to do it in real time. So far I have tried:

1. just moving every chord up or down the appropriate interval which is easy for some jumps (up or down a step for example)

2. analyzing the song with Roman numeral notation and then using that to play in the new key. This is easier if the jump is hard to calculate in my head quickly but is hard for some chords like V/III.

Are there other methods of doing this. I know whatever method I choose will have its pros and cons and they will all take practice but just want to know if there are other options and what the pros and cons are?

• A book on music theory or harmony theory would outline a set of basic approaches to transcription. Just moving everything up or down is, imo, the easiest to comprehend and apply on the fly. Especially for guitar. If you can play without looking at the hand you can read in A and play in D with no effort. The 2 approaches you have tried are among the standard set. Another is identifying the degree of each note in the key and finding the same in the new key.
– user50691
Commented Aug 11, 2019 at 13:55
• @ggcg “Another is identifying the degree of each note in the key and finding the same in the new key”. How is this different than Roman notation?
– b3ko
Commented Aug 11, 2019 at 16:46
• @b3ko - This is different from Roman numeral notation in that you don't need to analyze complete chord progressions--you just need to analyze individual notes. It's like translating the first notes of Beethoven's Symphony No. 5 in C Minor to 5-5-5-(b)3, then figuring out what those notes are in F minor. Commented Aug 12, 2019 at 6:27

A capo is one way.

Another is to know what the 'family' of chords are in each key. As in F and G in key C are like A♭, B♭ in key E♭, or E and F♯ are in key B. Takes a bit of learning, but when you consider that A>D>E is the same pattern as A♭>D♭>E♭, and C>F>G is the same as C♯>F♯>G♯, there really isn't the whole dozen to go through!

Another is the Blue Peter method - draw two concentric circles, one larger than the other. Mark as on a clockface with twelve note names, consecutively - C, C♯, D, E♭, and so on round each. Join in the centre. Inside disc is written chord, rotate outside one till it matches up with new key. Read each and every one off, inside to outside!

• I'm curious: why do you call this the "Blue Peter method"?
– lynn
Commented Aug 12, 2019 at 12:55
• @Lynn - in Britain, there's a tv programme called 'Blue Peter', part of which features making things for kids from string, tape, cardboard, etc, for next to nothing. Not associated with rolling one's own, or particularly a flag on a ship.
– Tim
Commented Aug 12, 2019 at 13:02

Another method I have used when transposing a piece to a different key and humming that is to shift the first note(s) up or down the appropriate interval, then use relative pitch (and the sheet music if available) to determine the rest of the notes by preserving the original intervals between them and the previous notes. For example, I can do this with humming the first notes of "O Christmas Tree" in F major by going C-up perfect 4th-same note-same note-up major 2nd-up major 2nd-same note-same note.

This is vulnerable to off-by-one errors (e.g. humming a minor 6th instead of a major 6th), possibly subpar sight-reading skills (e.g. forgetting to check for a key signature), and possibly a poor memory of the original tune (humming filler to get to the portion of the piece I'm familiar with may throw me off).

Transposing in 2 steps

You can transpose any note in the key of `X` to the key of `Y` using two simple steps:

1. transpose the pitch difference in key `X`
2. get the enharmonic in key `Y`

Example

In your example, you have the notes `C, F, G, D` and, `A` in the key of `C`.

Transposing to B

Let's say you want to transpose your music to the key of B. (1) The difference in pitch is -1 since B is a half-step below C. This means we flatten the notes first. (2) This also means we translate the degree of any note by -1 since B is one degree below C.

1. `Cb, Fb, Gb, Db` and `Ab` (transposed pitches in key of C)
2. `B, E, F#, C#` and `G#` (enharmonic degrees in key of B)