This is Avery Wilson, the best male singer I have ever heard, covering an R&B classic. You might be wondering why I pointed you to this cover when there is no guitar to be found. The reason is because Avery has said that he learned how to do riffs/runs and developed his ear by listening to and copying guitar solos with his voice. I've heard vocal coaches say that, when he sings, it's like he is playing his voice like a guitar.
I'd be really curious about you're take on what he is doing musically. Also the piano player in this cover is very good. The improvisation in this video is just insane.