We download Multitrack audio files from the internet and manually sort them.

References:

• Download Backing Tracks. Multitracks for Musicians and Sound-Producers! (isolated-tracks.com) 

• Download music, movies, games, software! The Pirate Bay - The galaxy's most resilient BitTorrent site (thepiratebay10.org) 

But the data set was not perfect as  there were also separated by some existing  audio separation methods.  Therefore, we sort the data set one by one and create a good data set.