A lot of the UK/AU and even USA companies buy from SBI. SBI was in america a few years back but they are now back in the UK. If you go to just SBI for music tracks you can compare tracks and will notice that a lot of their music is licensed out to other companies who pay to use it on their product. It cuts production time and costs of studio wages. The only downfall is that if I get a song, I would like to make sure the rendition is different.
For instance: Ameritz also buys from SBI and another company here from the USA. I used to get frustrated when I would buy different brands only to find the same track but with different harmonies on the song. Karaoke Versions is ok, but theyr CDG format is very blurry and looks bad when played. I liked some of Priddis Music's tracks. If you go to Priddis Music's site, they now have their CDG's for download. I'm not sure if you can use them in your shows though. I willl look more into that website for you