Yikes!
It is looking more and more like Yamaha have rushed this feature out unpolished and unfinished, rather than doing what they usually do, and perfect it for the Tyros series and let it trickle down, mature and well-developed a year or so later.
It definitely seems to cry out for the 1-2GB FLASH memory capabilities that the TOTL Yamaha's have, rather than a miserly 64MB, of little value if you are going to fill it up with audio.
64MB of flash memory would have been a great addition to the MOTL and BOTL to store MIDI styles in and have them instantly available, but if it is used up with audio, you are back to square one in needing to load up styles into the PSR like before.
I still think the USB stick loading of .WAV's for Multi-pad use is the cherry on this sundae. You should be able to do some SERIOUS modern loop production with these (most modern music is much more in chunks, without fills anyway) and break free from the time capsule arrangers seem to have got painted into.
Not a good omen, though. Both Yamaha and Ketron seemed to have stumbled, trying to mate audio loops with conventional arrangers. Firstly, it is always a question of CONTENT. 25 styles out of 400+ for the Yamaha (and apparently, an impractical loading procedure for new ones) and not exactly a blistering pace of new styles from Ketron (though FAR more initially, in their defense).
Then virtually closed systems, so next to impossible to make your own (lots of incredibly good drumloop libraries out there) to take up the slack the manufacturer leaves.
Two strikes, and the bases are loaded. Time to bring in a designated hitter!
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An arranger is just a tool. What matters is what you build with it..!