Move a progression to a new key

Write the original sequence clearly

Start with the constructed progression C–F–G–Am. Its final chord is A minor, so the small m matters. Before transposing, write the chord notes if you need a second check: C–E–G, F–A–C, G–B–D and A–C–E.

Transposition moves the pitches by a consistent interval. It does not rewrite the sequence into a new pattern of qualities. If a minor chord becomes major during a simple transposition, something beyond transposition has changed.

Move every root by the same amount

Raise the sequence by two semitones. C becomes D, F becomes G, G becomes A and A becomes B. Retain the original qualities, giving D–G–A–Bm.

The new note sets are D–F-sharp–A, G–B–D, A–C-sharp–E and B–D–F-sharp. Each sounding pitch has moved two semitones even when the written accidental pattern looks different.

Choose notation for the destination

A pitch-class shift alone can produce several enharmonic names. In a D-major context, F-sharp and C-sharp make the relationships easier to read than G-flat and D-flat. The sounding keys may match, but the scale-degree letters would not.

Read the destination key and chord spellings before saving. An automatic blanket rule such as “all black keys use sharps” is not enough for every destination. Flat keys need their own coherent names.

Separate register from key

Moving a progression to a new key does not specify the most comfortable octave for every instrument or voice. The chord symbols describe roots and qualities; the actual playback voicing also has octave choices.

Keep the same arrangement during your first comparison so you can hear the transposition itself. Afterward, adjust register or inversions deliberately. Treat those as separate edits, and check that every note still belongs to the intended chord.

If your source includes a slash bass, move that pitch as well. C/E raised two semitones becomes D/F-sharp: E moves to F-sharp while C major becomes D major. Transposing only the root symbol and leaving E as the bass would produce a different relationship. Check the bass label and the sounding note list together when preserving an inversion through a key change.

Use a return trip as one check

Move D–G–A–Bm down two semitones. The pitch relationships should return to C–F–G–Am. This checks that the shift was applied consistently and that the final minor quality survived.

A return trip is useful but not a complete proof of correctness: two matching mistakes could cancel out. Also inspect the before-and-after note lists. That independent view can reveal an incorrect accidental or a quality change hidden by a compact symbol.

Keep both versions when you are comparing

Name the original and destination versions in a way that makes the interval visible, such as “C exercise” and “D exercise +2”. Save the editable JSON when you want to return to the progression. A PDF can sit beside your instrument but is a reference, not a project editor.

No commercial song is needed for this exercise. A short sequence you assemble yourself is enough to practice keeping roots, qualities and written names aligned.

1. Enter C, F, G and A minor in that order.
2. Transpose upward by two semitones.
3. Check D, G, A and B minor against their note lists.
4. Play the complete sequence, then save a copy.