Vocal to Beat

[DJ Swydez]

Okay, I was listening to this DJ scratch and mix the other nite, and I am wondering if you guys know how to do what he was doing. He took 2 songs ("Show Stopper" by Danity Kane and "Do It to It" by Cherish) and faded them back and forth in a very unique way. He only had 2 turntables. "Show Stopper" was playing, but them all of a sudden the vocals of "Do It to It" started to fade in and the vocals to "Show Stopper" started to fade out, but the beat to "Show Stopper" was still playing and the beat to "Do It to It" was not there. Then he reversed it all of a sudden and the vocals of "Show Stopper" came back, but to the beat of "Do It to It". Then he scratched it up and "Do It to It" started playing normally. Does anyone know how he did this? I tried to do this on my buddy's turntables, but I found that I could not fade out only the vocals or only the beat of a song. Any ideas? I thought it was pretty awesome.