They have obviously spent time learning the instrument and how to make it shine, and are beyond simple chording and/or playing over commercially produced midi files.
Ian
And what the hell do you think you are playing over when playing an arranger? Professionally produced midi files!!! well duh!!....
They are just smaller, and in the case of Yamaha, far more boring. Unless one adds ALL the sampling and other NON-standard sound parts that some users spend WEEKS on adding and refining.