I used to play standing for all live gigs, and also for basic duo stuff, but once I got the extensive foot controls for automatic use, I started to sit... It coincided with some knee issues from the twist you have to do to run a couple of sustains and stand, and playing that way for eight hours a day or more!
So now, I've got lazy and sit 100%..! Mind you, at my height, not too many can tell if I am standing up or sitting down anyway! My keyboard height only changes a couple of inches for either.
I simply like to keep a very busy LH, I feel guilty relegating it to simple chord shapes every few beats and button pushing... I have always felt that, If I COULD play a part, I SHOULD play the part, so that makes leaving my LH free for a lot of button pushing a guilty pleasure! So I'm MUCH more likely to be trying to do a good comp with my LH and leads with my right than letting the machine comp for me.
Add to that a LOT of LH bass work, and you rarely find time from playing the LH bass to go push Variation and Fill buttons. A foot controller simply make more sense for ME... But if your playing style is just chord input and RH solos, then there's PLENTY of time to hit the buttons.
Back in the organ days, we would hit thirteen or more switches with our feet to play an entire bassline! I just don't see what the problem is, hitting a measly seven or so on just part boundaries!
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An arranger is just a tool. What matters is what you build with it..!