Torrents from the MLP Music Archive, which was active from 2012 to 2013 (with a separate release, possibly from a different party, in 2015).
Help Wanted: Rainwater Tornado is not seeding Version 13 because no other seeds or file downloads are available to obtain the data. If you have this torrent, please consider seeding it.
Version 16 is from the Brony Music Archive’s Tumblr post. (It’s unclear if this is actually related to the previous versions, but it’s included here for convenience.)
Versions 15 and 14 are from Ponyville Live!