Not really true. There's so much live material out there to listen to. Even in his 50's no one could sing or scream like Chris. His technique was one that required warm up, risk and singing very loudly to find or connect his mix, it's different from fry screams or singing cleaner or softer like a Lambert or a Mercury where there's more security.. the distinction became clearer as he got older and he toured a lot. There are accounts from someone who worked in studio with him in 2009 and said he was the loudest most powerful singer they've ever heard but the that he needed to warm up or break in his tone. The distortion just sounded different with age and his access wasn't as "clean" and so the natural vibrato became less common than coarse screams in different contexts at the top end of his range. There is no statement, record or evidence of him ever had having vocal surgery other than a clear mock parody article on a site called the dallas observer. Chris would have been touring solo from 1999 through 2000 and then recording with Audioslave in 2001. He sounds identical on both Euphoria Mourning and the first Audioslave record apart from a clear stylistic approach (grittier choruses, intimate verses) on the latter meant to differentiate their sound from his work with Soundgarden. He generally changed his style per record anyway, as he did with Soundgarden - he was a creative guy - his character and mix evolved often to move past what he did before. Euphoria Mourning was very Jeff Buckley-esque. He never "fucked up" his voice. He took a break in 94, sounded nearly the same in 95 (Superunknown era mature mix) then burned out and got very sloppy in 96 before cleaning up and sounding closer to how he did in 95 in 97. He needed a break absolutely and his top end access wasn't as clean but it wasn't a big deal. Down on the Upside and Euphoria Mourning showcase a very a deliberate sort of bluesey shift for him as a singer that is more than constant belting in the stratosphere. He got older.