This is what happens with an Internet post from six years ago. It gets rotten !

I've got the collection file recently as part of my quest for RIFF RMID files containing both SMF and DLS data. The "mega.nz" link doesn't work anymore, but the magnet for the bittorrent protocol still works. The file is 1.02 GB and has nearly 130,000 files of varied quality.

By the way, the files have all the '.mid' suffix, even when they contain something else. For instance:
40 files should be named with the suffix '.wav'
226 files are RIFF MIDI files, and should be named as '.rmi'. None of them include DLS data.
From the rest, there are 127,543 true SMF files, and 670 other things.

You can still access it using the Wayback Machine.
Hover over a highlighted day then click the time of the snapshot you want to view.