ScoreShift reads the staves, clefs, key signatures, notes and accidentals on the photo, then rewrites the page itself for another instrument: every note slides to its new line or space, accidentals and the key signature are replaced, ledger lines regenerated. The layout, beams, slurs, dynamics and lyrics stay exactly where the engraver put them. Everything runs on this device.
Or open a PDF, such as a score or part from IMSLP: pick a page, or export the whole file transposed as a PDF.
Best results: printed music, flat page, whole width of the staff in frame, even light. Check the Interpreted view and tap anything it got wrong.