The prayerful nature of Catholic songs and songs as a means of healing are not contradictory.
We Catholics do use songs for worship but some are not aware perhaps of the healing power of some of our songs, especially chant.
Katherine Le Mee writes a book on Chant and its healing powers. In it, she recounts of a monastery in France that dropped its chant routine. Within a year, the monks’ health declined. Their normal routine of work and prayer became too much for them. They became tired and prone to illness. The abbot allowed meat back into their diet, but it helped them none. Monks laid about like wet rags. A doctor came in and noted their hearing had declined. Ears play an important role in simulating the brain, and chant carries with it an energy that vitalize and strengthens the monks. The doctor prescribed that they return chant to their monastic routine. Chant more than an incidental facet of worship, plays an instrumental role in sustaining the monks through low hours of sleep and a rigorous schedule of work, study, and prayer.
Chant becomes a food in of itself in the monastery. It is no surprise that monks have used it for 1500 years in their monastic life.
Your friends are right and wrong. Our songs do have healing powers but we don’t consciously use them solely for that. Our first thought is worship. That in itself, however, can be a form of healing, supernatural healing, e.g. “Kyrie, eleison,” “Let All Mortal Flesh Keep Silent,” etc. You might argue then that we do think of our songs as a means of healing. That’s a stretch, but I might say to your friends, “there’s a healing aspect to our prayers, true, but most Catholics think of our songs as a means of praising God and uplifting our souls to him.” Not many are aware of the physical medicinal quality of chant and songs.
Our songs differ in that we direct them to a higher power, God, namely. Our hymns have a supernatural quality to them. We ask God for forgiveness and graces. We thank and praise Him. That’s the obvious difference in our hymns from mere Eastern vocalization. Your friends are agnostic, however. It’s difficult to defend the difference between Catholic song and Eastern mere vocalization when your friends are not sure if there is a God. You might have to defend the existence of a God, first. Just my thought there.