If you liked the part where he held the orchestra chord while he played a piano arpeggio over it, be aware that a lot of keyboards can accept a second hold pedal which can be tasked to ‘sostenuto’ which does the same thing. It will hold a chord, single line, whatever, and allow you to play staccato or held over the top of it. And any keyboard that does seamless sound transitions (Roland’s have had this for decades) can do the same trick of changing sounds (or even Performances) while the original sound sustains.
I agree with Jonny, he’s a great player, and whatever keyboard he plays will impress. But he IS trying to sell you one, so research his claims carefully, they may not be as good as his playing!
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An arranger is just a tool. What matters is what you build with it..!