(I binge watched the avengers recently and I came up with this idea after watching the scene between Loki and Natasha. Enjoy!) 

Loki paced back and forth in his cell, already bored of being trapped in the hands of the avengers. You were one of the avengers best agents, one night while you were scouting the ship you stopped at Loki's cell. Making sure he wasn't doing anything stupid. He somehow sensed you were there, causing him to stop pacing. He smirked before turning around to face you. "There aren't many people who can sneak up on me." he said. 

"You knew I would come." you said. Loki chuckled. "Yes." 

"Tell me, why stop here. Coming to check on me?" he asked, smirking at you. 

"Out of all the agents Fury could ask to watch you he chooses me, god I hate him for it." you said. crossing your arms, shaking your head with a sigh. Loki chuckled. "you're lying agent Y/N." you looked up at him. he was still smirking at you. 

"Ok fine, I don't mind it. I just....I just wish Nat would do it instead, I have a life outside of working for the avengers ya know. That was taken from me too soon." you sighed. Loki sat down finally. "What was this life?" he asked. "for once you're not trying to do anything stupid, or start a fight." you thought to yourself. 

"Why start a fight when there is no reason for it at the moment." he said. his voice a bit lower than before. 

"Well, before I worked for SHIELD I uh.... I was a musician. A rockstar. I had a band where I sang, toured the world, performing the biggest shows in front of thousands upon thousands of people. It is a life I wish I could return to. But knowing my own brother I cannot do so." you explained. "I was about to go on a tour with the bands that influenced me to become a musician, but I'm afraid that did not happen since I got pulled here." Loki nodded. suddenly a smirk came to his face. you rolled your eyes. "Loki stop doing that please, you're making me uncomfortable." you said. trying not to laugh. 

"Why not? you have a beautiful voice I see." you blushed. "Well, I do but, I'm not gonna sing if that is what you want." 

"Please? sing me something. do that and I will be on my best behavior." he said. you couldn't say no to that. you turned off the security cameras for a moment so you could sing to him without getting caught. "Alright just one. you better promise me you will go to sleep after this, I don't want to be kept awake all night." Loki agreed to this and you sat down in a chair. you thought of a good song to sing and began to sing the words. Which really surprised Loki.

https://youtu.be/iwIjvEonJdQ

the words really captivated him in ways he had never felt before. from what he read in your thoughts he knew you were a rockstar who could really sing agressively, but he didn't know you could sing in another way. 

When you finished the song Loki was staring at you in awe. "That was beautiful! thank you." he said. you nodded. "Of course, and I appreciate that thank you." you blushed before changing your expression to a more serious one. "Now go to bed, for gods sake."