What I'm generally saying is that the mapper could increase the AR at a certain point to fit in with the song. For example, say a song uses AR 9 and has some slow parts. Sometimes even an AR 10 song with slow parts seems unfitting to the song. The mapper could decrease the AR in the slow parts to fit in with the song, or if the song is building up (dubstep songs?) the AR can slowly be increased to be really fast (would work well with streams). I feel like this could be helpful with certain mapping techniques and open up new ones. It could also be more enjoyable to play.