The producer said he was in LA to record the
vocals for "Black Velvet," so she was probably just singing to a track. The vocals for BV were recorded at the same studio Adele wrote "Someone Like You."
Quote:Adele and I first met at Harmony Studios in Hollywood, California. It’s a small studio on Santa Monica Boulevard with a terrific Yamaha C7 piano and a great all vibe. Adele told me she’d been working with [producers] Fraser T. Smith and Paul Epworth. She played me a few songs, including “Rolling in the Deep,” which I thought had a weird title but sounded amazing. Adele also said she wanted to play me some clips of the singer Wanda Jackson, so our engineer Phil Allen went on YouTube from the studio computer and we listened to her for the next 40 minutes. I was struck by how Adele was firing me up with music from 50 or so years ago that had nothing modern about it. There were no synthesizers or four-on-the-floor kick drum beats—it was just this amazing, old, rockabilly kind of music that set the tone for the two of us to do something totally simple and heartfelt. It was a strange and inspiring way to spend our first hour together.
...At times, she had an almost historical perspective on songwriting, saying things like, “A great song at this point would have a line that is more general and about life, as opposed to one about the story itself.” She seemed to understand how great songs were put together.
More:
http://www.keyboardmag.com/artists/1236/...-you/29171