Ancient music

Of the hymns last Sunday in church I noticed that I most liked How Great Thou Art in preference to the more modern ones from Mission Praise. I got to thinking about older music. BBC Radio 3 has The Early Music Show and emperor used to present a great local radio show with similarly early music but I wondered how much further back we can go. For religious music, with my background in Christianity I naturally thought of the mysterious cantillation signs for the Book of Psalms. Some searching online finds me CDs by Esther Lamandier which perhaps I ought to investigate. I don't immediately find an easy way to sample them though I guess there are probably also other relevant artists.