I found this great public domain Acapella on Wikimedia Commons and wanted to share it with you.

It is recorded and beautifully sung by Magdalen Kadel alias Makemi. The original text is by either Leonin or Perotin.

Lyrics:
Breves dies hominis
mundi vita
humane propaginis
que sit vita, cogita!

Nitimur in vetitum
caro contra spiritum.

Pelle moram propera
mora non est libera.

Mundo nil immundius
que facis, fac citius!

Corpus, quod corrumpitur
animam persequitur.

Et bonum propositum
revocat in irritum.

Alios quod doceo
ipse docens impleo.

Christum ne exasperem
pauper sequor pauperem.

Corpus meum corrigo
et in servum redigo.