"There was religious music and there was the music of common people. They did not cross any lines and kept to their selves the main ingredients. pre-harmony music (let's say pre-bach) is very, very hard to enjoy. This is why you rarely find it in music concertos."
ummmm, how much 'medieval' music have you actually listened to? i mean, de gustibus non disputandem, but you might do well to consider that this sort of music has a very large and active following globally that certainly is not limited to specialists. but i'll grant you that it'd be a little strange having sackbuts and crumhorns on the stage one moment, and a full 19th century-type orchestra the next. 'don't know if i'd really enjoy hearing Beethoven say back-to-back with early polyphony... would certainly make for a strange concert aesthetic...
also, outside of the notre dame school (ie leonin and perotin) most sources that we know of actually had considerable cross-over of elements. (this is generaly considered why there was so much contemporary debate over the use and nature of music at all within a sacred context). Think of somebody like Dufay who was not only prolific within both genres, but functionally used the same elements of composition for both as well. This seems to be more typical than not of the known sources. further, it seems that not only were secular and sacred 'styles' interwoven, but that sephardic and arabic influences also were an important part of the musical tapestry across the iberian peninsula decidedly and into the rest of christendom by extension.