Start with semantic notation
Export an uncompressed MusicXML file from the original score. Each pitched note contains a letter step, an optional chromatic alteration and an octave. This tool changes those values rather than moving printed symbols on a PDF.
Review the edited file
Choose a semitone interval and an enharmonic preference. Traditional keys and harmony roots move with the notes. Explicit accidentals preserve pitch but may make the score busier; your notation editor can respell and simplify them.
Lyrics, prose directions and chord diagrams are not transposed. Check those manually when they mention a key, fret position or note name. Keep the original score until playback and parts have been reviewed.
Try a predictable interval
Choose Transpose the example score and enter 2 semitones. Its C4–D4–E4–G4 phrase should become D4–E4–F#4–A4, and the C-major key signature should move to D major. Download the MusicXML, open it in your editor and play it. That small reference helps distinguish a tool problem from an unusual source-score feature.
For your own score, choose Transpose MusicXML and select an uncompressed .musicxml or .xml file, or paste its source. Positive values raise pitches; negative values lower them. A shift of 12 semitones moves notes one octave while preserving their pitch classes. Notes outside the supported MIDI 0–127 range are rejected rather than wrapped into another octave.
Inspect what does not follow pitch automatically
The output keeps rhythms, rests, ties and existing document structure. It is not a new engraving pass. Review lyrics that name notes, spoken chord instructions, diagrams and fingering suggestions because they may still describe the original key. If the score contains tablature, altered tuning or microtonal alterations, use the originating notation editor’s transposition tools instead of removing information merely to force this conversion.