That's fascinating. I wouldn't have expected a band like Aerosmith — already with a capable lead guitarist — to bring in a couple of anonymous ringers!

Here's one you might find interesting; it's actually a guest vocal. I didn't include vocals in this article since there are a ton of examples out there, but this one was kind of cool; I was hearing it all the time but never registered it.

Pull up Kenny Loggins' "I'm Alright". Fast forward to about 50 seconds, and you'll hear a vocal that sings something like "Oh, now, headed for a better way!" Also at about 1:58, you'll hear the same vocalist singing something like "M-m-m-man, you make me feel good!" See if you can identify that voice. He was unknown back then, but became a prolific solo vocalist soon after.