Separate the new key from the old recording
Choose the new key for a concrete reason, such as a singer's range or more comfortable instrumental voicings. Use AudioChords to transpose the chord display, then check the first chord and one familiar progression. Do not assume the original audio changes pitch along with the labels. If it does not match, rehearse the new key without that recording rather than forcing two keys together. Write the original and performance keys in your separate notes so later sessions do not begin with conflicting references. Confirm the singer can manage both extremes of the melody.
Relearn the physical transitions
A progression can keep the same harmonic relationships while feeling different under your hands. Identify the two hardest moves in the new key and play them slowly without an accompaniment pattern. On piano, choose nearby voicings instead of moving every chord as a large block. On guitar or ukulele, check whether your chosen shapes preserve the notes needed under the melody. If using a capo, record its position and distinguish shape names from sounding chords. Then add the rhythm and practice the transition into each move, not just the pair of isolated shapes.
Check details beyond the chorus
Run the introduction, bridge, instrumental passage, and ending in the new key. These are easy to overlook when the chorus sounds comfortable. Verify any bass movement or melodic fill separately, because transposing a chord label does not teach your hands a new single-note line. Perform the entire song without stopping and mark the places where your old muscle memory takes over. Correct those short passages before another full run. Finally, agree on the count-in and first sung note with any collaborators. A transposition is ready when the complete arrangement works together, not merely when the displayed chord names have changed.
Label the rehearsal version clearly in any setlist notes you share. A familiar title alone is not enough when several musicians have previously learned different keys or arrangements of the same song.