The performance was part of an exhibit of his visual art, which is quite spectacular as well. Witness his giant, useless accordion, or his album cover collages (but what's the middle album in this one, the one in between Michael Jackson and Roxy Music?).
From the liners:
Each piece is composed entirely of records by the artist after whom it is titled.
"John Cage" is a recording of a collage made by cutting slices from several records and gluing them back into a single disc.
In all other pieces the records were mixed and manipulated on multiple turntables and recorded analog with the use of overdubbing.
A hand-crank gramophone was used in "Louis Armstrong".
Christian Marclay – "More Encores"