Readers are almost always privileged to read/hear a Machado story. This privilege arises from the confession of a secret that weighs heavily on a conscience. The narrators often feel they must set the record straight. The mystery cannot be long suppressed.
In "The Nurse" (also translated as "The Attendant's Confession" in Brazilian Tales), the eponymous narrator writes his confession from his death-bed:
So you think that what happened to me in 1860 can be printed in a book? Do whatever you please, but with only one condition: do not divulge anything before my death. You will not have to wait long, perhaps a week, if not less; I am incurable.The reader asks for a story, and it is given, began in earnest, imparted in a unique voice. The story is of great human interest, a mock-display of unstable emotions and the ensuing crime of passion. The nurse is caring for the sick Colonel who has a serious attitude problem—"If he had only been grouchy, it would not have been so bad; but he was also mean." The nurse is honoring his own end of the bargain, telling the secret story in graphic details, another Machado quality. The reader will have to keep the story to himself, for it is a privilege to be told this by a nurse harboring a criminal past.
Look, I could tell you about my entire life, during which time other interesting things took place; however, in order to do that, one needs time, spirit, and paper, and I have only paper. My spirit is weak and time resembles a night lamp at dawn. It will not be long before the sun rises on another day. It is the sun of demons, as impenetrable as life. Good-bye, my dear sir. Read this and wish me well; forgive me for whatever seems improper to you. Do not mistreat the rue if it does not smell like a rose. You asked me for a human document, and here it is.... [Oxford Anthology, 61]
In "The Secret Heart", the reader is again privileged to encounter a secret heart. The opening is a domestic scene.
Garcia, who was standing, studied his finger nails, and snapped them from time to time. Fortunato, in the rocking chair, looked at the ceiling. Maria Luiza, by the window, was putting the final touches to a piece of needlework. Five minutes had now passed without their saying a word. They had spoken of the day, which had been fine, of Catumby, where Fortunato and his wife lived, and of a private hospital that will be explained later. As the three characters here presented are now dead and buried, it is time to tell their story without pretense. 
The true story is then recounted with characteristic linguistic verve and, as promised, without pretense. The pertinent details of a "love triangle" and "forbidden love" (favorite Machado topics) are laid bare. The reader is once more treated to priceless instances of beastly and saintly human behavior. The plot ambling along and to the point. The stories are generous in the serving of delicious gossip.
The sharing of a common interest tightened the bonds of friendship. Garcia became a familiar of the house. He dines there almost every day, and there he observed Maria Luiza and saw her life of spiritual loneliness. And somehow this loneliness of hers increased her loveliness. Garcia began to feel troubled when she came into the room, when she spoke, when she worked quietly by the window, or played sweet, sad music on the piano. Gently, imperceptibly, love entered his heart. When he found it there, he tried to thrust it out, that there might be no other bond but friendship between him and Fortunato. But he did not succeed. He succeeded only in locking it in. Maria Luiza understood—both his love and his silence—but she never let on. 
It's fascinating how that single paragraph propelled the plot from easy friendship to familiarity and then to love. Clichés are quickly embraced and also dispensed with, "gently, imperceptibly", the story is coaxed forward and the scene set up for the great conflict. Machado had a way with inner psychology, sometimes tactless, sometimes full of tact, always respecting the delicacy of human feelings. But he also had the propensity to mix the lyrical with the ugliest of human tendencies. "The Secret Heart" not only captures the unraveling of a secret love but that of corruption inside men. Readers had to endure a sickening description of animal mutilation. Within the spaces allotted to tenderness and infatuations, Machado had prepared a place for the baseness of humanity—"It was like a moral tapeworm, which, although torn into many pieces, always regenerated itself and kept on going." 
The mastery of Machado's fine short stories is contemporary. His words and metaphors are exquisite at the level of the sentence. A story is cut to the quick, exceptionally, efficiently told.
He came back to the house, and he did not go away. Dona Severina's arms enclosed a parenthesis in the middle of a long, tedious sentence of the life he led. And this added clause contained a profound, original idea specially invented by God and the angels for him alone. He stayed on, and his life went on as before. Finally, however, he had to leave, never to return. Here is how and why. ["A Woman's Arms", 78]
The "how and why" is the very resolution of the story in question.
The milieu and contexts of Machado are important in the appreciation of his shorts, all period pieces. His nudge to the years the stories were set in is a permanent marker.
Just imagine that it is 1813. ["Wedding Song"]
This was the selfsame explanation that was given by beautiful Rita to her lover, Camillo, on a certain Friday of November, 1869, when Camillo laughed at her for having gone, the previous evening, to consult a fortune-teller. ["The Fortune-Teller"]
Garcia had obtained his M.D. the year before, 1861. ["The Secret Heart"]
The above scene took place on the Rua da Lapa in 1870. ["A Woman's Arms"]
It was May 1882, and Venancinha hadn't seen her aunt since Christmas. ["Dona Paula"]
The lawyer died two years later, in 1865. ["Wallow, Swine!" and "Justice Unbalanced"]
The years don't lie but they might as well happen in 2016. Machado seems to be writing specifically for posterity. The mischief in his tales is the mischief a week ago. The active lust of his characters does not go out of date. His depiction of male and female, free and slave, old and young, wants and needs is astute. Irrespective of century, incorporated in each story is the tangibility of dreams and desire.