Diki,
In the Yamaha way of marketing things, they only release 25 audio styles with the S950 and then if you like to own some more you will purchase from them. Each premium style for the T4 are $.8.95. I guest that the audio styles will cost the same or even more.
Look like to me that Yamaha is going to have the AUDIO styles for their keyboards for themselves. No third party will be able to create audio styles because as read in page 27 of the Reference Manual, the audio part (Drums) can't be deleted, edited or created from scratch from and for a Yamaha style.
Big difference with the Audya, where you have a bunch of audio drums kits and you can replace one kit from another in a style or even convert ANY midi base style into a audio drums style.
Well, that is Yamaha. As a user you like it or leave it. I respect their way. Maybe don't agree with some of the parts, but ................... they really make great products and have a way of testing that they usually don't have many bugs.
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Machetero