Transposing from 3 sharps to 4 flats

I am trying to change a song that is in 3 sharps to 4 flats (as I am better in flats). The original piece in 3 sharps has several extra flats, sharps, and naturals and, of course, I believe I need to change those particular notes.

• So, if the original (3 sharps) has a note with a flat beside it, what do I do with the note when I play it in 4 flats?
• And, if the original has a note with a sharp beside it, what do I do with the note when I play it in 4 flats.
• Lastly, if the original music (3 sharps) has a natural sign beside a note, what do I do with the note when I play it in 4 flats?

I'm probably not explaining well, but I hope you can understand my questions.

• A lot of music is printed with accidentals that are spelled incorrectly. For example, an editor might think that Bb would be "easier" to read than Bb, despite the fact that A# is more likely to occur in 3 sharps than Bb. This significantly complicates your task at transposing. Posting an example of a few bars with flats will help us determine if you are working from a "correct" original. If you are not, you will struggle when following the answers posted below. Commented Nov 6, 2022 at 18:28

Transposing from 3 sharps to 4 flats is equivalent to lowering each note by a half step. This means that:

• double sharps --> sharps
• sharps --> naturals
• naturals --> flats
• flats --> double flats
• It can happen that this takes you so far around the circle of fifths that you have to translate back from flats to sharps. If you transcribe a piece in A major that has a section in D minor, you should almost certainly notate the transposed section in C♯ minor, not in D♭ minor. Commented Nov 4, 2022 at 8:47
• @KilianFoth - The case of the isolated D minor chord in A major getting transposed to A flat major is debatable, though - I suspect quite a lot of publishers and Classical-/Romantic-era composers would actually use a D flat minor chord in that context (see the use of B double flat major chords in Schubert's Impromptu in F Minor, D. 935, No. 4 as the Neapolitan of A flat major). Commented Nov 4, 2022 at 11:32
• @KilianFoth Your solution to your hypothetical issue creates a problem. D minor is the iv of A so it makes more sense to use a few extra flats because if you use C# minor in Ab you will have an +iii. Commented Nov 4, 2022 at 16:36

Key signature of 3 sharps puts it in key A (and/or F♯m) Reading the piece as if it has four flats puts it in key A♭ (and/or Fm). The same can happen with E (and/or C♯m) and E♭ (and/or Cm).Except the other way round. In fact, were there no accidentals in the piece, it'd be simple to read each (interchangeably) as if the key signature was whichever you wanted - no need to re-write!

What's happened is each note has dropped by a semitone. So, the 'standard' (key signature notes and naturals will all go down by that semitone, any sharpened notes as accidentals will be naturals, and any flats (unusual in a sharp piece, but not impossible) will be double flatted.