I had Casio keyboards back in the 80s so I have always appreciated arranger keyboards. They are really just a regular synthesizer combined with an AI driven MIDI sequencer that follows your playing. It's not really very hard to understand but I guess people that aren't familiar with them are mystified by them. I am actually puzzled why ALL synths don't come with arranger abilities because it probably doesn't cost the manufacturer barely anything to include it in the ROM. There is really no reason why the entire Yamaha Motif range don't all have the ability to have onboard arranger styles. I guess it is just a marketing decision.