How to do it, step by step · Transposition · Music theory
First find the interval, from the original tonic to the new one. From C major to D major it is an ascending major 2nd. Then write the key signature of the…
How to do it, step by step
First find the interval, from the original tonic to the new one. From C major to D major it is an ascending major 2nd. Then write the key signature of the new key, and move each note by that interval, checking that the number is always the same.
The accidentals are the delicate part. An accidental raises or lowers its note relative to the key signature, and in the new key it has to do the same: what was raised a half step stays raised and what was lowered stays lowered, even if the sign is a different one.
Going from C major to B♭ major, F♯ becomes E♮: the E of the new key signature is flat and has to be raised. E♭ becomes D♭. If in doubt, check the interval note by note.
A trick, and a table for checking
The simplest transposition is by a chromatic half step: just add a sharp or flat to everything. From C major to C♯ major, the notes keep their names and the key signature changes. It is also worth checking the accidentals one by one.