one use is karaoke cd or dvd. Original arrangements don't depend on repetitive patterns and 7k lead voices work surprisingly well with recordings of real instruments. You lose left hand control naturally but can sound "just like the cd" which some people like.

With earlier machines I used to use a portable diskman, then a tiny 1GB mp3 player into line in, with the 7k it's very much more convenient getting the track you want if you are that way inclined, since the correct audio track can be loaded with the sequencer, even if the sequencer is just a control track to automatically change lead voices and effects without an actual played lead.