Robert Plant was heavily influenced by the Blues and played in many Blues Bands. He eventually ended up in The Band Of Joy with John Bonham. When Jimmy Page first heard him sing, his soulful moans gave Jimmy chills and he wondered why he wasn't famous already.
His singing comes from more than his throat, it comes from deep in his soul and you will know what I mean when you listen to When The Levee Breaks. You can hear him ride the beat in Black Country Woman, or his deep southern negro voice of the 1920's in Bring it on Home. He also is one of the few Vocalists who can carry an acoustical song and not make it boring.