Lohengrin is a 1840 opera by Richard Wagner (1813-1883) based on a German Arthurian tale. Proust hugely admired Wagner, and it is thought that the epic scope and length of some of his operas influenced the epic length of Proust's own work. Vittore Carpaccio (c. 1460-c.1525) was a Venetian painter who studied under Bellini.
Le son de la trompette est si délicieux,
Dans ces soirs solennels de célestes vendanges,
Qu'il s'infiltre comme une extase dans tous ceux
Dont elle chante les louanges.
And so deliciously that trumpet blows
On evenings of celestial harvestings,
It makes a rapture in the hearts of those
Whose love and praise it sings.
(Translated by Roy Campbell, Poems of Baudelaire, New York: Pantheon Books, 1952)
For the complete poem, plus English translations, see here.
This scene marks the first of the narrator's epiphanies on his road to becoming a writer. (Although the madeleine scene appears earlier in the novel, this scene happens earlier in his life). For most of In Search of Lost Time the narrator is struggling to find a subject for his writing. The Search is the result of this struggle.
This section stands apart from the rest of In Search of Lost Time. The narrator disappears as a character, telling instead of Swann's love for Odette. Some have suggested that this was Proust's attempt to show that he could write a conventional novel, if he chose. However, it is closely tied to the rest of the Search through its themes of love and jealousy, and through its depiction of French society, in the scenes at the Verdurin's salon.