I`m almost positive that the BK-7M and the new BK-5 , use a much newer sound set than the Prelude.

The only really great sounds are the organs and synth and a couple of pianos sounds are useable.

For the most part the sounds and styles on the Prelude need way more tweaking than Yamaha.

I think the reason I like my Prelude is for the organ sounds , IMO , they are better than the Tyros 3 I had.

I mean no tweaking necessary good !! , The T-3 had good organ sounds don`t get me wrong , I guess just different !
The Prelude organ sound are more realistic or I`m tone deaf !! LOL

In the end it is just a matter of taste and personal preference.

Later

Gary