The problem with vocalists in prog is that a great percentage of the musicians are classically trained in their respective instruments but the singers not (At least in singing), so the difference between a well trained musician and another not trained is evident, despite the natural vocal range.
Classic music (One of the main influences of Prog) is mainly instrumental and chorale so the only classical training for singers would be Opera, honestly I don't know any Prog' vocalist who had operatic formation, except maybe Annie Haslam and Francesco di Giaccomo from Banco who I believe have some training in Italy and Freddie Mercury who I'm sure had formal musical education in India and read somewhere was part of a classical choir (Not sure of this last one).
But people forget that despite this classical influence, Prog' is mainly Rock, in this case a tenor would be too much for the genre and probably would almost never sing in a popular music band (Except after they made enough money with opera like the three tenors).
But bands like Genesis, Yes, ELP, Jethro Tull, Kansas, Rush, Pink Floyd, etc, wouldn't be the same without vocals.
Iván
Edited by ivan_2068