Maybe Harry plays a lively, upbeat song that lifts the mood in Sirius's house. The magical atmosphere of the place seems to come alive even more. Sirius and any other characters present, like Remus, start dancing or at least tapping their feet. It could be a moment of pure joy and a break from the usual gloom and doom in their world.
He could be playing the piano as a form of therapy. In the fanfiction world, Harry has been through so much trauma. Playing at Sirius's house gives him a sense of peace and belonging. The music fills the rooms, and Sirius just sits and listens, realizing how much Harry has grown and how strong he is, despite all the hardships he has faced.
Well, Harry might play a very energetic and upbeat piece on the piano that makes Keshar want to dance. It could be a moment of pure joy and celebration between them.
In fanfiction, when Harry and Ginny meet Sirius, Sirius might offer them some sage advice on dealing with the dark forces. He could share his experiences about fighting Voldemort and his Death Eaters. Maybe he would see the potential in Ginny and encourage her to further develop her magical abilities, as he has always been supportive of Harry.
Well, perhaps in the fanfiction, there is an old piano in the Room of Requirement. Harry and Ginny find it while exploring. Ginny starts playing it and the music has a calming effect on the entire Hogwarts. Harry joins in and they create a new harmony that helps to solve a mystery in the school, like a hidden curse that was causing problems for the students.
In a more complex plot, Harry could be part of a prophecy that involves him using the power of music from the piano to defeat Voldemort. He has to learn special musical spells and collaborate with other musical - inclined wizards and witches. Along the way, he also has to face challenges from those who think music has no place in the wizarding world and wants to stop him from using the piano as a weapon against the dark forces.
Perhaps when Harry goes to Hermione's house, they end up having a deep conversation about their future in the wizarding world. They could discuss their plans for after Hogwarts, like Hermione's dreams of reforming the Ministry of Magic and Harry's thoughts on teaching Defense Against the Dark Arts at Hogwarts. They might also share some personal feelings they've been hiding from each other.
They might start by choosing a color scheme. Maybe they'd go for Gryffindor colors like red and gold to show Harry's house pride. Sirius might use his magic to move the furniture around easily while Harry decides where to put his Quidditch memorabilia. They could also add some protective enchantments around the flat while they decorate, making it a safe and cozy place.
Well, Sirius might see some of his own qualities in Harry's boyfriend. Maybe the boyfriend is brave like Sirius was, and Sirius would then start to warm up to him. He could share some of his old Hogwarts stories with the boyfriend, which would help the boyfriend understand Harry's world better.
One possibility is that their meeting is a vision or a dream - like encounter. Harry could be drawn into Azkaban in his sleep or through a magical object. During this encounter, Sirius could give Harry advice on how to deal with the upcoming challenges at Hogwarts. He might warn Harry about certain people who can't be trusted and offer his insights on the growing dark forces.
In fanfiction, when the Weasleys meet Sirius, there could be a lot of excitement. Sirius might share some of his wild adventures from his younger days. The Weasleys, being a large and warm - hearted family, would likely welcome him with open arms. Maybe they would exchange stories about the wizarding world, especially those related to the Order of the Phoenix.
In some fanfictions, when the Dursleys meet Sirius, there could be a lot of chaos. Sirius, being a wizard, might shock the Dursleys with his magical abilities. They would probably be terrified and try to get away from him as they are not used to magic. Maybe Sirius would try to take Harry away from them right then and there, leading to a big confrontation.