This song is written by the worship team at Trinity Anglican Mission in Atlanta, Ga where worship pastor Martin Reardon and other gifted leaders work and serve. Reardon is an excellent musician, writer, and a down-to-earth, genuine guy with a longing for worship music that connects to the liturgy of the service (more of Martin on youtube).
This song comes from the “Prayers of the Saints” CD that they put out in 2006. My good friend Jarrett Dickey (http://fiveriverschurchplant.blogspot.com), who worked at Trinity during seminary brought this song (and many others) to my attention. I have greatly enjoyed getting to know Marty, the good people at Trinity, and their carefully crafted music. (please check out excellent worship music site http://www.trinityworshipmusic.org )
At the Emory Wesley Fellowship, the United Methodist Campus Ministry at Emory University, we sing this song often 
during communion because of the simple, but profound words and melody and the meaning behind them. The worship team (cello, mandolin, piano, drums & guitar) have a great time with St. Thomas.
The text of this song is adapted from a Eucharistic prayer of St. Thomas Aquinas (12th century) and with its modern musical setting can used from a prayerful, solemn vibe to a medium tempo setting of simply offering thanks to God. There are much better recordings out there, but this should give you an idea of how it can be played and done.
Rev. Dr. Joseph McBrayer 