This is an excerpt from an article on uncredited performances in Billboard, August 11, 2010:
http://www.billboard.com/column/char...ory?tag=hpfeed
[Barry] Scott cites a song that entered the Hot 100's top 40 32 years ago this week as a contrast to today's more complex music industry.
"When 'Whenever I Call You 'Friend' ' by Kenny Loggins was released on Columbia in July 1978, Warner Bros. didn't bat an eye that one of their biggest stars was a very noticeable uncredited special guest: Stevie Nicks. (Although the part was originally going to go to Loggins' co-writer, Melissa Manchester, the authors agreed that Nicks would be better suited for the song).
"Once (such appearances) became common practice," says Scott, "it was too late to go back for a variety of monetary and legal reasons."