Once, promenently posted on DT, there were instructions on how to contribute tunes by either mailing muscial scores, or by preferably creating midi files.

It gave details on the format that was desired.

Sarendipitously, in the process of searching for instructions I found at the bottom of the "MC links" a mirror site for DT that has standard scores,ABC,whistle, and midi files. Digital Tradition Mirror Site

I would like to assure that the tunes I would like to contribute are in the desired configuration. I am sure the information is here somewhere.