My Yamaha keyboard has what they call Performance Assistance Technology which up until recently I rarely used. The manual says it works with Songs/Midi files and specifically midi files with imbedded chords and melody like the included songs and other midi files like XF files. You can take a regular midi file and with PRSutility compute chords and it will work also.
I rarely play with midi files and almost all of my playing is with auto-accompaniment with styles making PAT next to useless for me. I play a few midis that don't seem to work well with auto-accompaniment because they have rhythm changes during the song or whatever and then I might use PAT.
However, the other day I "discovered" that PAT works with auto-accompaniment as well, although it doesn't seem to be documented anywhere. As long as you are in the Chord Mode of PAT and play chords with your left hand with a Style you can improvise(cheat?) to your heart's delight with your right hand. This makes it handy for an amateur like me to add an interlude, scale, instrumental, etc. to a song where I couldn't before. I know you pro's are really groaning at this but maybe someone else can find this useful like I do.