Led Zeppelin wasn’t just good at writing music as a band but exceptional as individual artists. Their ability to stand out alone and as a unit led to their massive success throughout the 1960s and ‘70s. Each member was a master of their instrument; in Robert Plant’s case, his instrument was his voice.

Fans of rock music everywhere are always quick to praise Robert Plant—and rightly so. He has an entirely unrelenting voice, as he seamlessly performs some of the most challenging vocal tracks ever written. Songs like ‘Stairway to Heaven’, ‘Immigrant Song’ and ‘Babe, I’m Gunna Leave You’ are vocal mountains that some of the most talented singers could never climb, but Robert Plant made it look easy.

“I saw Zeppelin in ’69 and that was transformative. As I would put it, that was god’s work,” said Paul Stanley when recounting the first time he heard Plant perform. “When you see a band that are so tied to each other and the synergy within the band and not only the music, but the sexuality of the band. Everything was so potent and so perfect that was a transformative moment for me.”

Stanley continued to describe Plant’s vocals as “mind-blowing.”

Because people were drawn to Plant’s vocals, they could tell when his voice began to change in the mid-70s. When the band released the album Physical Graffiti, fans noticed his voice was growing more raspy than usual. Given how much of their performance rested on his voice, onlookers grew concerned that it might impact Led Zeppelin moving forward.

There was a reason his voice started to betray him. Led Zeppelin was massively in demand because of their success. To put their demand in perspective, the band played the biggest gig of all time in the Tampa Silverdome. Not only was the gig a sell-out, but it was also one of the quickest sell-outs of all time. The band played to 70,000 people, setting a record that wasn’t broken again until 2013.

This should give you an idea of how much people worldwide wanted to see Led Zeppelin live, which meant that they were touring a great deal, with Plant singing for days on end and hardly warming up before shows. On top of that, while on tour, Plant was drinking and smoking a great deal, all of which eventually deteriorated his vocals.

Plant managed to make it work, though. He leant into the raspiness of his voice in these newer albums and has since managed to carry it over into his solo work. While his voice doesn’t sound like it does in the early Led Zeppelin songs, he still has a great voice that can sell out venues worldwide. Losing his voice was inevitable, given the way he sings, but the fact that he makes this new tone work exemplifies why he is so good.