When my son was much younger, he went through a phase of pretending that things were his babies, so I looked into getting him a doll. (He grew out of the phase before I ever got around to it, but that's beside the point.) I was particularly struck by the Waldorf-style dolls. In addition to being beautiful and handmade from natural materials, they typically have very minimal facial details. This allows the child to impart various emotions to the doll, as the face could easily seem to be happy, sad, etc. It made a lot of sense to me that to a sad child, a grinning doll would not be a comfort, but a Waldorf doll would seem to share a child's joy and sorrows.
Today, it struck me that one can draw a parallel with the liturgy. I went to Mass with my heart heavy with sadness for the recent losses in the Real Learning community. I simply could not participate in contemporary, wave-your-hands-in-the-air, tambourine-filled music. But that is what I got. It was like having a grinning doll mock my sadness.
I believe that traditional hymns are the Waldorf doll of liturgy. Certainly, there is joy in them, but it is a deeper, reflective joy that can be engaged in even in the depths of sorrow. Of course, there are some contemporary songs that would fit the bill to some, and certainly we should not ban all songs that are more overtly joyful.
I am neither a theologian nor a liturgist, so maybe I am way off-base here. But it just seems to me that this is something to consider when deciding what music is appropriate for Mass, and another reason to follow the Church's instruction to give traditional music primacy in the liturgy... one more reason to put down the tambourine and pick up a hymnal.