Why do some people cry listening to an opera sung in a language they don't speak? What about wordless syllables where the emphasis is on the voice as instrument (melisma)? Obviously, it's the style and the melody, the emotion in the performance, and lyric meaning can be married to the musical meaning, but some would argue (in the case of opera, especially) that music with words merely detracts from the music, putting it in a supporting role. A mortal sin if one is of the mindset that music is what the other arts aspire to.
Rand's writing on graphic design (the decorative arts) versus pictorial painting can shed light on this:
The task of the decorative arts is to ornament utilitarian objects, such as rugs, textiles, lighting fixtures, etc. This is a valuable task..but it is not an art in the esthetic-philosophical meaning of the term. The psycho-epistemological base of the decorative arts is not conceptual, but purely sensory: their standard of value is appeal to the senses of sight and/or touch.
She adds that if a work of art has to be representational, "if it does not present an intelligible subject, it ceases to be art. On the other hand, a representational element is a detriment in the decorative arts: it is an irrelevant distraction, a clash of intentions. And although designs of little human figures or landscapes or flowers are often used to decorate textiles or wallpaper, they are artistically inferior to the nonrepresentational designs. When recognizable objects are subordinated to and treated as a mere pattern of colors and shapes, they become incongruous."
Is the above true for music and lyrics as well? The answer depends on whether or not music is to be considered representational or not. It's a debate that's raged for a long time, and probably saw it's most dramatic battle in the field of opera. Disney's Fantasia was another battlefield where music not only competes with a libretto but with animation (continuing Wagner's quest for the "gesamtkunstwerk." (In the case of Fantasia, the battle between Disney and abstract animator Oskar Fischinger, the battle was between abstract and representational art, but the question still comes down to the same as the one between lyrical versus "pure" music.)