Who originally sings the song "Hallelujah"?

I have a Performance to do this week and I need to know who was the original singer to sing the song "Hallelujah". I know there are many people who sing this song, such as John Cale, Jeff Buckley, Rufus Wainwright, Kate Voegele, Alexandra Burke, etc. My personal favourite is the cover by Kate Voegele, and I'm hoping I'll be able to get a "karaoke version" of it, but since she is not the original singer I'm not sure if that will be possible. Can anyone help me out? Who originally sings it?