How is the author's description of the music crucial to the story's theme in "A Wagner Matinee"?
There is a sense in which the way that passion of the music is described is contrasted directly with the kind of life that Aunt Georgiana has experienced over the last few years since she married and left the city to farm out in the countryside. One of the central theme of this story is the importance of music to us as humans, and for Aunt Georgiana, who was an accomplished pianist, to have been without music for so long was a terrible deprivation. Note the way that the description of the Tannhauser overture captures this conflict:
Then it was I first realised that for her thisbroke a silence of thirty years; the inconceivable silence of the plains. With the battle between the two motives, with the frenzy of the Venusberg theme and its ripping of strings, there came to me an overwhelming sense of the waste and wear we are so powerless to combat; and I saw again the tall, naked house on the prairie, black and grim as a wooden fortress; the black pond where I had learned to swim, its margin pitted with sun-dried cattle tracks... The world there was the flat world of the ancients; to the east, a cornfield that stretched to daybreak; to the west, a corral that reached to sunset; between, the conquests of peace, dearer bought than those of war.
Note the way that words such as "frenzy" and "ripping," used to describe the richness and the passion of the music, contrast dramatically with the barrenness and starkness of Aunt Georgiana's home. We understand the reality that Aunt Georgiana has lived and pity her for the way that music has been barred to her for so long.