HI: Fran
I don't know what left hand hold function your talking about,
but if it is to hold the left hand voice in the accomp.
it works great on the 9K PRO.
I have never had any problem with drums not playing styles correct &
I have alot of Korg, Roland, Solton, Gem, & Technics Styles converted
to PSR they all work great.
Don't know about playing sequences as I don't use them, only tried a few & they seemed to work OK.
As for the organ sounds the only noise I find in them is like the
noise my old Hammond organ with slide bars had if you set things up to sound that way.
I find this kind of noise on some Organ voices like Jazz Organ's etc. & if you turn down the Low EQ you can get rid of that to.
I also have a dual 31 band EQ, Plus 10 band EQ on mixer, 3 band on powered speakers + the 5 band in the KB so it does make the KB quite versatile.
Enjoying the 9000 PRO
Denny