Here is outline of the next talk I want to give. Please invite me! I will speak for food and drink.
Two models of song
1) The classical model
The text comes first. Song is a musical setting of a previously written poem.
The relation between music and words is fraught with tension. The composer in some sense is going against the poet. The text's own prosody is over-ridden by the music.
2) The vernacular model
The listener processes music and words at the same time, without caring which was written first. We don't think of song as a musical setting of a "poem." The words might come first, or the music; it doesn't matter too much. If we asked Cole Porter whether he wrote music or words first, the answer might be interesting, but it wouldn't really affect our understanding of his songs.
The lyrics may or may not have a "literary" value apart from their union with the music.
There is no fundamental tension between words and music.
A third model: in vernacular settings of literary poems, we know the text comes first, and was chosen for its literary value. The inherent tension of the classical model comes into play again.
Thus the classical model is more relevant, despite the vernacular character of the setting. This means that we listen to this kind of vernacular music differently than other genres. The poem is not anonymous, unlike a folk song.
Consequences of this for Lorca. He arises out of a tradition in which the vernacular assumptions are operative, but settings of his work need to be heard more critically, with this analytical separation between words and music.