Sometimes sacred music began not as an expression of our longing for the Devine or for the Christian Mystery. Instead, some had wholly irreligious origins but were then commandeered by someone who felt the music was appropriate for liturgical use. Here are a two pieces that went through a conversion of a sort, and made the crossover from secularism to religious.
The first one is an "Ave Maria" using the famous "Intermezzo" from Mascagni's Cavalleria Rusticana opera. You can't go wrong with Bocelli.
The next one is "Lux Aeterna", taken from Edward Elgar's Enigma Variations.
You may want to turn up your volume for the next two since they're a bit low throughout their duration.
Please ignore the poor quality of the video and concentrate on the music.