I am always happy to receive suggestions for adding pieces to the site. When the suggestion is for a published piece, I go the source (a score or, for out-of-copyright pieces, a .pdf). I apply quality control since being let down in the past when I uploaded a file unchecked only to have pointed out later numerous errors therein.
So the answer is a Yes, with provisos. For out-of-copyright music there shouldn’t be too much of a problem; for in-copyright pieces expect the answer to be No, unless you are the composer.
Also note that I use the Sibelius notation program, so can accept files in .sib format; also I can accept MIDI and Music XML files for pieces out-of-copyright. If the files are in different format, they would need to be exported from the original program in Music XML format.