It is one of those ecclesial matters that comes up with some regularity.
No, opera is not appropriate for Mass.
No, a piano/ violin concerto is not appropriate for Mass.
No, an ordinary inspired by The Girl from Ipanema is not appropriate for Mass.
No, Let It Be and Sunshine On My Shoulders are not appropriate for Mass.
As a parish music director I found the distinction between sacred and secular was most helpfully put this way: “At your relative’s funeral Mass we should sing Church songs, not radio songs.”
Lest this seem snobbish, opting for highbrow vs. lowbrow tastes, the distinction could just as easily be made between Church songs and concert hall music, and often should be, for weddings.