Sibelius notation software for OS X can generate a MIDI sequence audio file (.mid, .midi) from it's own music notations saved as a .sib file. It s unlikely any other tool can reliably process .sib files, so this seems likely to be the only reliable choice for this conversion.
Convert Sibelius music notation to MIDI-sequention sound.
We found one software available in the database for this conversion.
Apple macOS / Mac OS X software - convert sib to midi on OS X
A music composing and notation software for Mac
Convert from sib file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.