Not very many Vocalists do that, altho a few "Yee-Owwwwww!" a short one or a melodic Bit here and there. I remember a "Tommy Lee's" Search for a Singer show,where a candidate was criticised for injecting a Harmonic "Bit" during the guitar solo. Once, years ago a buddy and I joked about Rob Halford sung the Guitar solo in "Jawbreaker" Live, as KK & Tipton glanced at him,hopign he'd stop mimicking the sounds.lol!