transpose for baritone sax

[Francesco Petrogalli]

Hi,

I have written a part using the orchestral pitch (real note) of an
instrument, the baritone sax (and other instruments, like trumpets,
alto, and so on).

All the parts are rendered with the real notes, so that I can listen
to the midi and check the music on the piano easily (I am no good at
transposing on the fly).

Now I need to produce the parts for the single instruments with the
correct transposition, but keeping the same pitch in the midi.

Is there already a facility to do so, say a function that I can place
in front of a music sequence and get it transposed for saxophone? or
do I have to come up with my own?

I understand that the correct way of doing this is first write the
notes in the tonality of the instrument, and _then_ use \transposition
to get the correct pitches in the midi, but I already have the notes
in the ly file with the orchestral pitch and I would like to avoid
rewriting the whole part.

Kind regards,

Francesco