This is "Be Thou My Vision" Hymn Tune SLANE arranged for String Quartet, vocal solo or congregational singing in the key of D and Eb. This is very simple and simple rhythm (piano or guitar) could be added as there is chorded lead sheet. - Great for a church service or wedding. Simple and reflective.
You can download the sample audio of this arrangement and a sample of the score. There are other arrangements of this tune by hansencharts.com here on this web site.