I think that, for me, it is sad that Yamaha have chosen this route. I can only imagine how good a Yamaha PSR could sound if the money spent on R&D'ing this feature were simply spent on creating (or even simply porting from the XF series) far better, punchier MIDI drum kits.
It is the path taken by most other manufacturers, to great success. Going the all audio route seems such a convoluted fix for a simple problem. And, as with any audio loop drum track, you lose many advantages that MIDI styles give you. You can't change the drumkit... a sticks style will never change into brushes, or a rock kit into a funk kit. Your style will never sound different with some simply editing.
And the drum patterns will never be editable... If you have a song where moving the backbeat around in one bar of the groove, or a slightly different kick pattern helps fit a song better, you are all out of luck.
I've been saying this since the Ketron days, but personally for me, I thinks audio loops are a technological dead end, with more disadvantages than advantages and improvements. Instead of this dead end, if arranger manufacturers simply made better, more detailed and punchy drum KITS, all of our current editing options still work. Current Korg and Roland arrangers have drum patterns that can sound quite close to real audio loops. And, if you listen to the demos of the better VSTi drum kits (BFD, EZDrummer, etc.) you can see a MIDI drumkit can be made to sound completely indistinguishable.
As ROM sizes gradually ramp up, more memory devoted to better drum kits will bring us virtually everything that features like Yamaha's audio styles give us, with NONE of the disadvantages.
That's a win/win, in my book.
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An arranger is just a tool. What matters is what you build with it..!