Don't know that it qualifies as rock per se, although over their time they played pretty much everything except metal (ugh!).

The Bee Gees 1974, before their later disco sound epoch, when Robin's vibrato and Barry's mid-range through falsetto voices and they were still young with all that amazing energy. In an era when live performance on stage with rudimentary gear by today's standards meant live, and with no metal distortion to hide behind with their vocal centric sound, talent definitely required.