Thanks! Yeah, definitely adds a new dimension to my "live" playing. Back when I had a home organ, with both the Wurlitzer and Yamaha models I had (the Yamaha was a D-80, and I think the Wurlitzer was called a 375, but not 100% sure on that), each of those organs had a 3rd mini solo keyboard in addition to the regular two keyboards most home organs have, which really helped to be able to bring in a different instrument without having to switch any buttons while playing. The solo keyboard on the D-80 even had portamento.
When I sold the D-80 and went with a multi-keyboard set-up, starting with my main keyboard being a Yamaha DX-7, then through a PSR-500, PSR-510, PSR-520, and now, my PSR-E433, I usually only had two keyboards -- the main one and a back-up. And I didn't really miss having the third keyboard too much, because unlike with the home organs, these newer keyboards all had programable presets of some kind, allowing quick and easy one-touch major changes to the sound. And except for the DX-7, they all had split keyboards, which made it like having three keyboards, anyway. But having that actual third keyboard, with its own set of capabilities and sounds which is not dependent on the settings of any of the other keyboards, opens up a whole new world of playing.
I did have a three keyboard set-up for a little while several years ago, with a 5-octave Casio CTK-691 on top. I think this keyboard only cost me about $130 back in 2003 (though the music store was matching an internet price -- may have been about $200 before the price match), yet it had all kinds of features -- dozens of effects like phase shifter, reverb, and rotary speaker; organ drawbar mode (though totally menu driven -- no dedicated sliders), hundreds of built in sounds, multi-track recorder, synth-edits like filter controls, and a really good sound. In fact, about the only thing that really kept me from making this a main keyboard was that there was no way to "freeze" the rhythm or style when switching registrations -- each registration had its own rhythm and tempo. So, if I wanted to change registrations in the middle of a song, then I needed to use a different keyboard as the drum machine. But anyway, when I stuck this keyboard on top of my set-up, I devised a kind of over-reaching bracket to hold sheet music, and it was just too high up to be comfortable. Whenever I tried to learn a new song and had to use sheet music, it felt like I was looking toward the sky to read it!
So, with this new set-up, while it's not obviously visible in the photos, the GAIA is actually on a sliding tray, and there are bars at the base of the front of that keyboard that can fold up. So, if I want to learn a new song that requires me to read music, instead of just learn by ear, then I can slide the GAIA back, fold up the arms, and then rest the sheet music essentially where I had it before I added the GAIA. If the music is in a rigid book, then I don't even have to fold up the support arms. Of course, that precludes me from using the GAIA while learning the song, but it's probably best that I add the bells and whistles and special effects after I get the basics of the song learned, anyway.