Morricone is a genius of arrangement and orchestration, always so fresh!
These are the kind of sounds I like a lot, but it's very unusual to find them anywhere as samples becuase they're not widely popular.
It's not hard to make something approaching it, but for an enthusiast it's always a bit disappointing because there's so much else that went to make the original sound. A Time & Love plugin might help....;-)!
here's a suggestion: try layering a fairly cheesy organ sound (not a Hammond, more a Farfisa-type) with a softish clavinet or spinett and then add tremolo, or leslie vibrato. (Precision Sound have a nice Philicorda organ at a great price, and there are probably plenty of VST OrganPlugins).
Using a valve-type compressor plugin, maybe also an amp simulator if you have one and a simple reverb -a plate or a medium room-also helps. You don't want much top in the sound either.
If you make some music with that, it'd be fun to hear it.
I think Nigel has this pretty well covered. The only thing to add is that the envelope shape of this sound isn't really the standard organ 'On-Off'. It sounds like the response is more like piano or vibes - no sustain, with a couple of seconds decay. I think some of the Yamaha stage organs used to have a switch to do that. In fact, some of them even had a few extra voices - including harpsichord- that you could mix in with the flutes...