Two different transformations
A transposing instrument can have a written note that sounds at another pitch. MusicXML records that relationship in a transpose element. Moving the composition to another key is a different operation from preparing a written part for a particular instrument.
Preserved instrument settings
Music Desk leaves instrument-transpose elements unchanged while moving written notes and keys. The resulting sounding music moves by the same interval. To convert a concert score into a clarinet or saxophone part, use an instrument-aware notation editor.
Tablature, tuning changes and microtones need further rules beyond chromatic semitones, so this tool rejects those cases rather than produce a misleading score.
Work through a transposing-part example
A B-flat clarinet part may contain written C4 with an instrument transpose value of−2 semitones, producing sounding B-flat3. If you shift that written score up 2 semitones here, its note becomes D4 while the −2 instrument setting remains. The resulting sounding pitch becomes C4. Both written and sounding music have moved up by the chosen interval.
If your goal was simply to display the same sounding music as a concert-pitch score, that is a different request. Changing written pitches and also clearing the instrument transpose setting must be coordinated. This tool does not guess which display convention your source uses or automatically convert a transposing part into concert notation.
Check every part after an ensemble transposition
A multi-part MusicXML file can contain different instrument settings in different parts or staves. The tool preserves those settings and shifts each pitched note uniformly. Open the score with your notation editor’s concert-pitch view both on and off, then listen to a unison passage. If parts no longer agree, inspect the source’s transpose encoding and instrument assignments before distributing new parts.