John Mayer may be singing along with his love Katy Perry in their new duet, “Who You Love,” but Mayer had the song in his head long before he met Perry and it wasn’t his idea to cast her in the duet. “I had this little chorus for years and it was, ‘You love who you love,’ and I thought that was always going to be a great thing someday,” Mayer, 36, said today on “Good Morning America.” “A song that people could hear and feel that sort of permission.” Mayer and Perry, who first made headlines as a couple last summer, debuted the song’s music video today on “GMA.” They star in the video alongside real-life couples who answered a casting call, as well as a mechanical bull. “It’s just so authentic,” Mayer said. “There’s nothing scripted in that video except putting a bull in the middle of the desert.” ABC