Once while I was backstage at a concert, B. B. drew me aside and sat down with Lucille on his knee plugged into a small Fender Champ. He said something like, “You know what? I tried to play slide like that and I couldn’t get the hang, so I learned to make the sound with my fingers like this…” and, playing the intro to Elmore’s ‘The Sky is Crying”, he demonstrated how he would bend the string and “trill” it (as he referred to finger vibrato) to emulate a slide guitar.