Here, Don Quixote does his best to convince an embittered and deeply skeptical Alicia Quiroga as Aldonza -- or rather his beloved Dulcinea, as he sees her, of his reason for being there. But it's to no avail, and she storms off -- until that is, he mentions his quest. "Quest?? What quest" she asks. And he explains his "Sueño Impossible."
I'm not bowled over with the interpretation that Senor Langlais gives the crazed Don. To be fair, I don't understand Spanish, but I nonetheless find his performance very matter-of-fact, almost nonchalant, without the drive that pushes the distressed fever inside him. Once he gets into the song, however, I think he ratchets things up slightly, and adds a wistfulness to his performance.