A more recent example, but I find it rather bizarre that there are so many people out there who think that 'Valerie' is a Winehouse song. I love Winehouse, but I was really fond of 'Valerie' when the Zutons first released it one year earlier. It's a little frustrating that it's never on the radio anymore. And it's formally not even Amy Winehouse who is the sole credited artist on the re-working of 'Valerie', as it is first and foremost the brainchild of Mark Ronson, with Winehouse being the featured artist. The whole album Version is chockfull of similar covers (perhaps most notably the Kaiser Chiefs' 'Oh My God', sung by Lily Allen, and The Smiths 'Stop Me If You Heard This One Before' with guest vocals by Daniel Merriweather).
[youtube]http://www.youtube.com/watch?v=L3xpmfJp0Xc[/youtube]
Also, but not that far removed from the famous version, here's 'Unchained Melody', first released 10 years before the famous Righteous Brothers version of 1965. There were actually a couple of singers who did 'Unchained Melody' in 1955, but my favourite is Roy Hamilton's:
[youtube]http://www.youtube.com/watch?v=o8Fuesi8VcI[/youtube]
It's called 'Unchained Melody' because it was the soundtrack to the 1955 movie Unchained; another forgotten little fact.
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clarity of thought before rashness of action