Hi Myzone,
I have a psr1500& it works with BIAB, using chord detect setting/external clock.
i had a look thru some of the midi specs on the cheaper current psr's , couldn't find the relavent function,
so guessing they probably won't work.
They don't appear to have good midi specs in regards to Receive function.
Below link to Yammie Manuals
Page 209 for PSRS710 manual states it has the chord detect function like me psr1500.
I'm guessing that the higher tomid end keyboards, like tyros, psrs910,710,900,700,3000,1500 have trhe better midi specs.
Download the manuals for the keyboard that yo might be considering & just make sure it can sync to external clock & that part of it's receive functions, it has Chord detect.
I haven't used my setup in a while as I mainly have it midied to my Korg PA3x, but I think my setup might have been easier than above. I think I just disable the Receive for the midi channels that Corresponded to
BIAB songs , so that all that was sent was the chord channel> I'd have to double check that though.
http://www.yamaha.co.jp/manual/english/result.php?div_code=