Horovitz said that he is still devastated by the rapper's death earlier this month at the age of 47 following a long battle with cancer.
Copyright: Rex Features Everett Collection
In a candid interview with Rolling Stone, he said: "My wife is like, 'I want to make sure you're getting it out'. But then I'm walking the dog and I'll start crying on the street - it's pretty f**king crazy."
Of the hip-hop icon's role in the group, Horovitz added: "Yauch was in charge. He was smarter, more organised. In a group of friends, you all come up with stupid s**t to do. But you never do it.
"With Yauch, it got done. He had that extra drive to see things through. We each had our roles. One of his was the make-it-happen person."
Watch the video for classic Beastie Boys track '(You Gotta) Fight for Your Right (To Party!)' below: