Comcast is adding another X factor to its Xfinity X1 pay TV service: YouTube.

The nation’s largest cable TV provider, later this year, will add Google’s streaming video network to its X1 system, available in 50% of its 22.5 million homes.

YouTube content will show up alongside other on-demand content and be searchable using the X1 voice remote. Comcast CEO Brian Roberts demonstrated YouTube on Xfinity X1 Monday at Morgan Stanley’s Technology, Media & Telecom Conference in San Francisco.

He showed how a search for The Voice, the music reality show from Comcast-owned NBC Universal, included online-only The Voice YouTube videos in addition to scheduled NBC broadcasts. And his voice search quickly found Buzzfeed’s video of making a watermelon explode by wrapping it with rubber…