If you prefer to hear your part being sung rather than just played on the piano, you'll want to check out this free site - SavedSounds.com. Thanks to Rebekah M. for sharing the link.
All of the Messiah Choruses are included, with synthesized voices singing. The part you select plays out the left channel and the other parts and piano accompaniment play out the right channel so you can change the balance to your preference. The website is very easy to use, though you aren't able to change the tempo. Some of the songs are tediously slow, but many are at a reasonable tempo. The files are downloadable.
Even if you don't need the extra practice, I recommend giving the site a try, just to get a good laugh out of hearing synthesized voices singing Messiah.
by Sara
