You'd think rock singing would be easy: masked by guitars, surely all you'd have to do is marry macho d*ck-swinging on stage with some sexually charged or angry lyrics. But it's a lot more nuanced than that - even if some people have made a good living doing just that.
Some singers - like James Hetfield and Lemmy - have the perfect voice for their band's sound, but that doesn't necessarily mean they're the greatest of singers. They're characterful and inspiring, of course, but in traditional technical terms, they're quirky at best.
And though modern rock singing on the whole has split quite noticeably between pop punk whining and that atrocious cookie monster growl that sounds like a joke nobody ever gave the punch-line for, there is a vibrant classic style "revival" that defies such gimmicks. Because for all the guitar riffs and thundering drum solos, the voice as an instrument and a tool of performance is just as important to rock and metal music as it is to any other genre.
It is the door to the emotion of the song, the call to arms and the element that carries the greatest capacity for nostalgia. Thanks to the unique environment it is created in - competing with loud, electronic instruments - rock singing is also a hugely powerful thing, and the medium can inspire some incredibly gifted singers.
But who deserves to be counted as the elite? Close absentees: Simon Neil (Biffy Clyro), Lindsey Buckingham and Ozzy Osbourne.