The Goldberg Variations are one of the great virtuoso keyboard pieces so you would expect that it would take a guitar duo to perform them. And a pretty accomplished guitar duo at that. But we live in surprising times. Here is a performance of the Aria, the Canons and the Quodlibet from the Goldbergs on solo guitar by Marco Salcito:
Ok, pretty impressive. But that is surpassed by this recording by Jozsef Eotvos of ALL the variations:
Now as we don't have a video it is possible, I suppose, that portions were double-tracked, but it doesn't sound like it to me. Notice that he is playing an eight-string guitar which makes the bass lines a lot easier. Of course he takes the tempos considerably slower than we hear on piano or harpsichord. But as there are no tempo markings in the original, this doesn't seem an indictable offense!
I am reminded of a story I heard about Canadian/American jazz guitarist Lenny Breau who met one of his idols, Chet Atkins, backstage one day and mentioned to him that he, Lenny, had struggled a long time to master this one particular solo on one of Chet Atkins' records. Chet Atkins looked back in amazement and said, "hey, I double-tracked that solo!"