The XD9 does incorporate features from the SD1 that I think are important .
#1. The ability to instantly remov all parts of a midi sequence ,except for drums + bass .....is a nice feature . I put an Elton John midi sequence in and play piano to that sequence with the bass and drums only . I just think that the drum bass feature is a nice tool . Save alot of time having to edit sequences . You get this feature with the XD9 + XD3 .
I really like the idea that the XD9 is less weight . 7lbs makes a difference .
I also like the layout of the intro/endings + fill ins better on the XD series vs. X1 .

The only thing I miss on the XD series is portamento + aftertouch .

Ok .....that's it for now . dano
danosmusic@yahoo.com