Here’s some food for thought: people seem to like devotional, sentimental music at Mass whether or not it relates to the day’s readings or the awesome sacrifice of the Mass itself.
The truth of the matter is that properly speaking, liturgical music has the texts of the liturgy as its wording. In fact, the first time the phrase “active participation” was used in a papal document was in Pius X’s 1903 motu proprio Tra Le sollecitudini in which he asked the people to sing Gregorian chant of the texts of the Mass (Kyrie, Gloria, etc) and therefore participate in the action of the ritual, the goal of which is the glorification of God and the sanctification of man.
“Active participation” meant doing the liturgy itself rather than busying oneself with the rosary or Marian hymns as worthwhile as they are. (It certainly didn’t mean busyness for the sake of inclusion or to blur the lines between laity and ordained).
In other words, devotional activities were for devotional times; liturgical activities were for the liturgy.The important phrase in the pre-conciliar liturgical reform was “don’t sing at Mass, sing the Mass.”
Although “O Little Town of Bethlehem” is a great devotional meditation on the Nativity, it isn’t really liturgical. Every Mass has proper texts for the introit (opening), offertory, and communion that relate to the readings of the day. There is no need to put an overlay of “We Are Called, We Are Chosen” or “Eagle’s Wings” on the Mass when the Church already gives us proper texts for these things. Although hymns are permitted in the Mass, the proper place for devotional hymns is in other liturgical and paraliturgical events–novenas, Liturgy of the Hours, adoration, praise festivals, etc.
For a good book on how to take baby steps in this direction in your parish, see Christopher Tietze’s writings on the matter. Also, Fr. Samuel Weber, OSB distributes free via e-mail his Gregorian chant settings of the proper texts of the Mass for each week. To join his mailing list, e-mail him at email@example.com.