It's unfortunate that Dio is much less known than Ozzy, considering he was a more capable singer, never gave a bad performance ("We don't drink when we play"), and wrote almost all the lyrics he sang. Fortunately, his music has received attention from various vocal coaches on YouTube. If you want to check out his vocal longevity, listen to his performance of "The Mob Rules" at the Radio City Music Hall in 2007. https://youtu.be/BTxSNosJrDo