The program that creates .capx files, Capella music notation software allows for import of instrumental music in form of a MIDI format (.mid, .midi) and thus makes midi to capx conversion possible. Unfortunately, we do not know about any other program that can convert midi to capx at this time.
Convert MIDI-sequention sound to Capella music sheet.
We found one software available in the database for this conversion.
Microsoft Windows software - convert midi to capx on Windows
A music notation software
Convert from midi 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.