“Katz” samples the Emerson, Lake and Palmer song “Blues Variation” and “The Hut of Baba Yaga” from their 1972 album “Pictures at an Exhibition”. Another segment of “Blues Variation” is sampled mid way through “Katz”.

“Blues Variation” (1st Sample):
https://youtu.be/P0E5krom__M?t=1m37s

The Hut of Baba Yaga":
https://youtu.be/xMdwIP9vRWs?t=50s

“Blues Variation” (2nd Sample):
https://youtu.be/P0E5krom__M?t=2m8s