This is from the opening of the show. I've edited out the odd opening, which follows the overture and opening credits. Either this was a slightly trimmed down version for television, or they wanted the TV audience to be more informed about what was going on, but they have a narrator in a business suit sitting by the stage and talking to the audience. He does a lot of that during the opening, what looks like he's introducing who each of the characters are. But I've jumped past that, deep into the opening sequence.
To earn money, Miguel Cervantes worked as a tax collector, and hhe and his assistant have been arrested and thrown into prison for taxing the kind's property. His fellow prisoners dive in to take his possessions, but he fights to keep one thing, a manuscript. The bullying ring-leader of the prisoners is about to throw it in the fire, when Cervantes offers a compromise -- to please the "kangaroo court," he offers a diversion, to tell the story that's in the manuscript and use the prisoners to play the parts. When the ring-leader says it's a waste of time, Cervantes chides him that time would seem to be the one commodity they have plenty of. The other prisoners agree, and Cervantes heads into his trunk and says, "I shall impersonate a man, Alonzo Quixana..." and the story begins as he tells them, "I, Don Quixote.".
(For some reason, it appears that I might not have been able to edit out the end of the clip, so it's possible you may get to see a bit of that odd narrator.)
Here then is Jose Maria Langlais as 'Don Quijote' from the 1974 original Chile production of El Hombre de la Mancha.