Happens during the first series, before Annie learns about what Owen did.
AU where Aidan Turner can actually sing because we know from The Hobbit that he couldn't sing to save his life.
He lies in bed, legs crossed by the ankles, a cigarette between his fingers. It's his day off and he's going to spend it as humanly as possible: doing nothing. It's a beautiful day, though, the sun bright and high in the blue sky of Bristol, warm and comforting in his room. He could go out and enjoy such a pleasant weather, but he feels too lazy for that. The smoke slowly comes out of his mouth and is immediately answered by a little cough that makes him roll his eyes and smirk. Annie and he both know she can't actually feel the smoke in her lungs but she complains anyway, out of habit, as she keeps roaming the room. It might be a nice day, but with the light falling on her dark skin, making it golden, and that smile on her lips, Annie is more radiant than anything else.
It is the East and Juliet is the sun.
She goes through his book collection on the little mantelpiece, her finger lingering on the covers as she looks at the titles. He's tried, weeks ago, to have her understand he sometimes needs his privacy and his room to himself but "my house, my rules". So he lets her haunt the bedroom, all in her curiosity, and keeps an eye on her as he smokes. She moves from one side of the room to the other, now interested in his old vinyl records, a happy smile on her lips.
"Oh!" Her little exclamation of joy has him raising his head to focus on her. He doesn't have to ask, knows the explanation as to such a noise will come in the next seconds. "My grandpa loved this song, used to listen to it all the time!" She takes one of the records, flips it between her fingers in a way she must have seen in movies, and he wants to tell her to be careful, those are original, fragile objects, but it would make him sound old and annoying. And, because it's Annie, he lets her do as she wants. Soon, she puts the record on his turntable and the first notes of the song come out of it.
Louis Armstrong's La Vie en Rose, of course. "Satchmo was such a great performer. That show in New Orleans in the 50's... Unforgettable!" She gives him that look, the one when she's forgotten he's actually way older than he looks, and he grins smugly with his cigarette in his mouth. "But don't get me wrong, Piaf's version is better."
She rolls her eyes but says nothing, and continues her inspection of his room in silence. It's not awkward or uncomfortable, the nice silence of two people getting along and simply enjoying each other's company, and soon Mitchell lets his thoughts drift away, eyes to the ceiling. The song comes to an end at some point but she doesn't pick another record to listen and he doesn't feel the bed moving as she sits next to him. It's a weird feeling, knowing she's here but not feeling the air moving around her or the gravity affecting her, and it's something he's never really got used to with ghosts.
She sits cross-legged by his side, staring at him and it should be uncomfortable but, as everything else when it comes to Annie, it's not. "Do you know how to play all these instruments?" Her eyes go from the guitar to the saxophone to the squeeze box, frowning even slightly.
"No, I simply keep them and pretend I can." He laughs as she hits him, even if he can't actually feel the punch on his arm. "Of course I can! You'll realise soon enough eternity can be quite long and boring sometimes, you need to keep yourself busy."
He doesn't tell her he could already play the accordion when he was still human and that he used to play in the trenches, to cheer up the troops. He doesn't tell her he's actually started playing the saxophone after said live performance of Armstrong. He doesn't tell her playing the guitar helps flirting and flirting leads to sex and sex leads to drinking. Sometimes, things are best left unsaid.
There's scepticism in Annie's eyes, as if he were known to be a professional liar or something (true, but not when it comes to such normal trivial details). He rolls his eyes, crushes the end of his cigarette in the ashtray and sits straight. "Okay, give me the guitar."
She squeaks and claps her hands and he can't even make fun of her, she's too adorable for that. He tunes the guitar, thinking about what he can play for her until he remembers this one song that keeps playing on the radio and that she likes to sing when she's making tea or doing the dishes. And, indeed, it takes her only a few notes (and him whistling) to recognize the song and, much to his surprise, she starts singing softly, and he follows her in the duet. She keeps smiling and he grins back, and it's such a perfect moment. He doesn't think about the consequences, about the lyrics they're singing like they mean it. Thinking is for later.
Home is wherever I'm with you.