Answer:  As many as it can get (provided they’re good . . .).

It is, surely, one of our towering achievements as a civilization – right up there with the Sistine Chapel, the B Minor Mass, Notre Dame, Paradise Lost, . . . [suggestions for additional items welcome].  That something so tightly constructed – so bound up in its own formal, quasi-mathematical structure – can be so incredibly beautiful is one of the Great Mysteries. If you don’t know the piece, you really should get to know it – and if you do, you know what I’m talking about.

I don’t think you can do much better than starting here.  Yes, it’s my son – and No, that’s really not why I think it’s terrific. I’ve been a little Goldberg-obsessed for many years, and I think I’ve heard most if not all of the commercially-available recordings  (and some not-commercially-available ones as well – how about a bootleg Rudolf Serkin from Vienna in the 1920s!), many of which are quite wonderful – and I think Sam’s version holds up really well, and has its own very interesting things to say about the music; I particularly love the way he gets the “swing” of the dance movements, and you won’t hear a more achingly beautiful version of the final “aria da capo” anywhere.  Plus, his eight little introductory conversations/demonstrations are quite interesting too.  Ten bucks well spent, in my opinion – if you listen all the way through and don’t agree, let me know and I’ll refund your money . . .