Note that 32 tracks that were included in the first torrent were no longer available on the SXSW website as of the release date of the second torrent. That list is here for reference.
These torrents include all the tracks that could be previewed on the SXSW website for SXSW 2013 as of March 7, 2013. This year's collection includes 1,210 files totaling 7.39GB. Note that the filenames and ID3 tags have been updated to properly reflect the artist names and song titles.
The first torrent was seeded February 21, 2013 and the second on March 7, 2013.
If you need a good BitTorrent client, I suggest: feedback if you enjoy these torrents.
Disclaimer: This site is in no way affiliated with SXSW or any SXSW artists. These torrents are provided as an alternate means to sample the songs available on the official SXSW site.