This sheet music (Mozart) is public domain and can be found HERE

Scroll down the page until you see K.626 (Requiem). Number 11 is Benedictus and has sheet music plus MIDI. These are pdf files so you'll need Acrobat Reader to see the music and/or print it out but if you don't have Acrobat, you can download it directly from this site. It is a beautiful song--and I hope you impress the pants off your friend with this. :)