Back-up Vocal~ The Backing Tracks album has held a place in the music industry for decades. As Bo explained, they are alternate versions of an album, with instruments such as lead guitar or bass taken out of the mix. Thus, aspiring players can practice improvising solos or crafting supporting music threads on top of real songs. My favorite example came from my man, Neil Zaza. He released a Backing Tracks version of his “212” album. A truly fantastic resource. The guitar solo has FINALLY made a comeback in the last few years. CDs that allow a player some room to create them are a welcome tool. It was quite neighborly of Sir Neil to make not just 1, but 9 such albums available.  
I opine that a DBS 3 Backing Tracks CD, provides an extraordinary challenge for a player looking to throw their hat in the Retro Space Rock music arena. Prepare for the sale of variant releases devoid of other instruments as well. After all, the band has a Winnebago to fix. Buckle up.