The trick is, once you decide to play along with an SMF, all KINDS of things become possible, even on your one keyboard arranger. Yes, having a 76 is a bit of a plus, but I am sure that, as long as changing one sound on a Part doesn't cut off the previous one (love that about my Roland's), the sequence itself can do some VERY complex things to fairly basic playing. Add to that the ability to easily change Registrations (again, without cutting off played notes) or OTS settings with foot controls can eke amazing things out of your playing.
For instance, my G70 (hardly state of the art!) can stack up to SIX different Tones all on one note, all in different velocity ranges (if you want), has an extensive set of single Tones that are actually four-way splits (woodwinds, brass, strings, etc.), does seamless registration changes, without any sound glitches (if you are careful).
The thing is to get creative with HOW you play... For instance, drop the sustain pedal, and use sostenuto instead. Now you can hold pedal notes, high 'floaters' partial chords, open voicings, whatever, and then play 'normally' while they hold, and it doesn't turn to mush. Get VERY good at keeping your playing tightly inside a velocity range, and you can easily double or triple up what sounds you can play without touching anything at all...
A long time ago, I got my trusty K2500S and the Orchestral Board for it. There are a LOT of very well programmed setups that can make you into a virtual orchestra (Kurzweil's were pretty much the industry standard in orchestral mockups until VSTi's took over) by creatively switching sounds depending on touch or pedals. Most arrangers can get VERY close to the K's capabilities, and this, combined with the SMF adding in a few things you can't quite get to, or changing your sounds and setups while you keep playing, stuff like this is possible, IMO.
Trick is, though, getting the touch, the voicings, the approach to this full orchestral style down. Obviously, it's a lifetime's study to even begin to understand the orchestra, but select songs like this should be achievable if you have the technical chops.
Personally, I would have preferred to hear this organist perform an improvised piece on it rather than this VERY carefully crafted and worked out piece. After all, it's all well and good to pull this blockbuster out of your trick bag, but far more satisfying to be able to improvise in this style without pre-programmed registration changes and slavish following of an SMF.
Just don't put your arranger down... With work, you could achieve this, with more work, you can achieve even more. Add a MIDI keyboard to your arranger, double the possibilities. Add pedals, even more. Sky's the limit.
[This message has been edited by Diki (edited 09-08-2010).]