One thing the BK7m had that for typical Roland dmbass reasons they neglected to add on all the other BK’s is a nice simple ‘mirror keyboard mode’ that took one single channel from the sending keyboard, and mapped the entire Registration/performance including splits and everything to that single channel, vastly simplifying control by a master keyboard.

It’s a common feature on most other brands, and one more in a LONG line of common features Roland decided its users didn’t deserve. Just in case you needed more proof that Roland arrangers were designed by people who didn’t actually USE them!🤬