This was first drafted this past March as part of a Music Shuffle Challenge, for Drumming Song, by Florence + the Machine.

I've seen this AU done multiple times but at the moment I can only locate one, in The Hobbit fandom. (It is hopefully self-evident, but there's a bit more detail/explanation on the AU in the end notes.)

Derek raised his eyebrows as he took the last turn on the way up to his house and saw Stiles' Jeep sitting there at the end of the drive. He parked beside it and as soon as he got out of his car he could hear voices from inside the house.

. . .singing?

"Ohh, who's afraid of the big bad wolf, the big bad wolf, the big bad wolf. . . Who's afraid of the big bad-"

"Stiles!" Scott yelled, and Derek snorted. He wondered if it was the song itself Scott took exception to, or-

"It's stuck in my head, Scott! What do you want from me?" Stiles asked, and the odd beat that had been underlying his repetitive singing continued.

"For it to stay in your head?" Scott suggested, though if it was an actual suggestion, it wasn't one he sounded very hopeful about. "It's kind of . . . insulting, don't you think?" he added in a lower voice, though it was still clearly audible as Derek walked up the steps towards the front door.

"It's not like I'm saying Derek is the big bad wolf." Stiles said patiently, and Derek shook his head, trying to figure out why the banging clatter sounded familiar.

"I honestly wouldn't be surprised if you did." Derek said, folding his arms and stopping in the doorway.

Scott jumped - really? Derek sighed - and Stiles looked startled, his hands stilling. He had a pair of paint-stirrers in his hands - one of them painted with the rich sunset-orange Derek was refinishing the kitchen in - and had been banging them against the table. Drumming on it, Derek supposed. He shook his head.

"Well then, big bad." Stiles grinned playfully and Derek just arched a brow at his new moniker. "We had a couple of questions for you, that's all. Or," he kicked Scott's ankle, and he yelped, shooting a betrayed look at Stiles for it, "Scott does, I'm just here to make sure he asks them."

Derek's eyebrows rose again, but he nodded, walking inside. He put aside the nagging feeling at the back of his mind for the moment, focusing on Stiles and Scott before him.

Stiles was calm, though he fidgeted restlessly; both were usual. Scott's fidgets were more anxious and his heartbeat jumped unpredictably between faster and slower rates. He was often like this, though Derek didn't know why. It always put Derek on edge.

Derek woke up with the rolling, trancelike thrum of a drumbeat in his head, as he had for years. He closed his eyes again, trying to hold on to the warm, comforting yet thrilling feeling it gave him, but it was no good.

Heartsongs could only be heard in dreams, that was how it worked; there was no holding on to them past waking. No. . . No matter how much he longed for that feeling. He sighed, smiling slightly, rueful as it was.

Of course, most people's heartsongs were . . . singing. Derek had never been unhappy with his - though some of his family had expressed quiet concerns when he first spoke of it as a cub; only to be quickly silenced by his mother - he had always loved the throbbing, driving beat. But he supposed it might have been . . . easier to find his soulmate with the sound of their voice, than the drumming beat he had. In theory.

Even without seeking proof, without hearing her sing - as he had been denied - Derek's sharp ears would, too, surely have been able to recognise a voice that was not truly his soulmate no matter what lies it offered. Even if it wasn't- Voices could be similar, but not like the sound of drums, which could be produced by anyone. They couldn't really, of course, but there was no hint offered by the song as to who. . .

Assuming the drumming even was his soulmate; Peter had suggested a few times when Derek was young that he might hear it because there was no soulmate for him.

Derek's stomach turned sickeningly, and he sat up, folding his arms across his belly.

He'd never believed Peter before, not even when he was a child, Derek told himself that there was no reason to think now that-

Wait. Drumming. There had been something familiar- Familiar.

Derek threw himself out of bed almost in a stumble, tugging on a shirt and jeans, boots, barely thinking, just hearing echoes, and it only occurred to him when he was halfway down the drive that it was still the middle of the night and he shouldn't. . . Derek couldn't hold himself back, though, not when he could be so close.

It was hardly even a conscious decision to keep moving, to run.

Derek only hesitated when he was crouched on the roof outside Stiles' window. Though it was a familiar place to find himself - had he been . . . so close, so many times? For as long as he'd been back in Beacon Hills, had he been so close to- Derek swallowed thickly.

He watched Stiles through the curtains for a minute - he'd left them open - and then felt incredibly creepy about it, and knocked on the glass lightly. He told himself that if Stiles didn't wake up, he would leave and . . . and he didn't know. His head was still spinning.

Derek knocked again, and Stiles rolled over, his pale, freckled face coming into view, silvered by the moonlight. Derek froze, just as Stiles' eyes opened. He sat up, frowning, then turned towards the window after a moment.

His heartrate jumped, but not alarmingly - it occurred to Derek, not for the first time, that Stiles had been put through a lot by the supernatural in Beacon Hills, not least Derek himself, and handled it with amazing grace most of the time - and he cocked his head, lips pursing.

"Derek?" Stiles flicked the catches and opened the window, leaning onto the sill. "What's up, big bad?" he asked, yawning, and Derek's heart leapt. "Something explode? Death? Dismemberment? Disaster?" He rubbed his face. "You can come in-"

"Do you play the drums?" Derek asked, interrupting him, and Stiles lowered his hand, tilting his head even further to the side.

"Disaster, dismemberment . . . drums. Um. Is it important?" Stiles asked, eyebrows rising, though he didn't look upset.

". . .sort of?" Derek said shyly, pulling back. "I shouldn't have woken you, it isn't-"

"Yeah. Yeah, I play drums." Stiles said, and Derek's heart leapt. "Is it important?"

"I hear drums in my sleep." Derek said before he could think better of it. Stiles slipped, his arm propped on the windowsill giving way under him. Derek reached for him instinctively, but he caught himself without help. "I-"

"You hear- Your heartsong?" Stiles said weakly, his eyes wide. "Wait, you- you think it's me?" he asked, voice soft.

Derek swallowed. "I. . . I don't know. But today, when you were waiting at my house. . ."

"I was banging around, yeah." Stiles nodded understanding. "And it sounded like. . ."

"I- Yeah maybe. It was different - it's drums, in my head, not . . . that," Derek shook his head, "but it was niggling at me," he admitted, frowning slightly, because he'd had no idea why, "and then when I was asleep tonight, when I . . . I heard them, I woke up and I thought. . ." he trailed off, meeting Stiles' eyes again.

Stiles reached out and brushed his jaw lightly. "Can- Can you sing for me?" he asked tentatively, and Derek swallowed. "I'd play, but I don't have a kit any more, and it's like, four o'clock in the morning, so probably not the best time anyway."

Derek laughed self-consciously, flushing, and ducked his head. "I- I probably shouldn't have come. Not at, um. Sorry."

Stiles smiled, shrugging. "It's fine. I- I, uh, understand."

"You want me to . . . to sing?" Derek asked, and Stiles nodded tentatively. "So you- You think that yours. . . It could be me?" he asked, voice quiet.

"Could be, yes." Stiles said, then looked away, biting his lip. "I-" He met Derek's eyes again, confidently this time. "I can tell you. . ." He swallowed, fidgeting. "It's a werewolf singing. My heartsong. I was so confused before I knew werewolves were real, I can tell you." he told Derek. His lips pressed together, tilting crookedly into something that wasn't quite a smile.

Derek stared at him, trying to figure out. . . "How do you know?" he asked. He didn't think Stiles was lying, was mocking him, but. . . There was no way to tell a wolf from a voice, from a song. At best, Derek had thought - the little he had thought - Stiles might hear a man singing in his dreams - a man with a voice that could be his.

"It's . . . I hear howling." Stiles said, lifting his head again to meet Derek's gaze.

He opened his mouth, then closed it, shocked. Then, abruptly- "You want me to howl?"

Singing was one thing - and Derek was aware he might be subconsciously putting off doing it, nervous; what if his voice wasn't Stiles' heartsong? what- and he would have told Stiles that he thought Stiles was his- That his heartsong was . . . different. That he wanted-

Singing was one thing, but Derek couldn't exactly howl in the middle of town at whatever time of the night - morning - it was now.

Stiles interrupted his thoughts. "No, I mean- I hear singing, and howling, together. Sort of . . . not the same, but blended together." he looked awkward, stiller than usual. "Sometimes one's stronger than the other, either way, but it's always both." He smiled a little. "Don't really talk about it." he said, a little tight.

Derek licked his lips and. . .

He didn't really choose, only started with the first words that drifted across his mind. It was the opening to a wolfsong, a love song, one he'd learned as a child, and Derek flushed a little warmer as he kept singing. He was too afraid to look at Stiles, but he had to know, and. . .

Derek's voice wavered as he forced himself to look up from the windowsill. Stiles' slim fingers were curled around the windowsill, clinging to it. His arms were tense. And-

Derek's voice faltered entirely as his gaze reached Stiles' face. His eyes were wide and his lips slightly parted. "S- Stiles?" Derek asked tentatively, shifting his weight. He wondered if Stiles said . . . no, if Stiles told him it wasn't him, if he would just- Run.

He didn't know how far or how long, but he couldn't. . . He couldn't. . .

Stiles shifted, reaching for Derek, and he leaned a little closer, hesitant. Stiles threw himself forwards, leaning bodily out the window and pressing a kiss to his cheek. Derek wavered, wrapping one arm around Stiles and putting the other one down to steady himself, claws extending and digging shallowly into the roof to keep them both up as Stiles slipped the rest of the way out the window and fell into his arms.

"I. . . Stiles?" Derek asked, shaky.

"It's you, of course it's you, silly wolf." Stiles said, laughing a little, his eyes damp but shining. He kissed Derek's cheek again, then the corner of his mouth.

Derek hugged him tighter, a little in shock.

"I'll drum for you if you like, tomorrow." Stiles said, and Derek shook his head. Well, he would like, but he didn't need to hear it, he- He trusted Stiles' word - his reaction. Derek hadn't thought he would - could - trust someone's word again but- But Stiles. "There's a kit I can use at school. I do- I've never heard you howl from up close." Stiles continued softly. "I know I probably can't hear it properly, not like a wolf could, but. . ."

Derek was very much fighting the urge to howl now, but he was together enough to know that it was still a bad idea at this moment, this place. He kissed Stiles instead, sliding back to sit on the roof instead of crouching there, Stiles settled sideways in his lap. He let out a startled noise, clinging to Derek's shoulders, and kissed back, with a soft hum.

"I do want to hear you drum for me." Derek said, laughing under his breath, brow resting against Stiles'. "But I- You." He couldn't speak quite evenly. Or . . . sensibly. He nuzzled Stiles affectionately, his wolf shivering with happiness, a warm thrum in his chest, when Stiles laughed and wrapped his arms around Derek's shoulders, nuzzling back. Stiles' gesture was warm and soft, gentle but not shy, shallow breaths tickling Derek's skin.

"I want to howl now." Derek confided, swallowing down the tightness of it in his throat, nosing Stiles' cheek again, then kissing him lightly. "Finding you, having you- It's-"

Stiles' laugh was near-silent this time, and his smile was softer. He was laughing at Derek, at the wolf, but it was sweet, there was no sting to it. Silliness and perhaps surprise spurred the laughter, not disgust. Derek swallowed hard, closing his eyes and pressing his nose against Stiles' cheek again, breathing slow, calming himself and just . . . enjoying, both.

"Happy wolf?" Stiles asked, and Derek cleared his throat, nodding. Stiles cupped his jaw. "My happy wolf. Big, bad, happy wolf." he said lightly, thumb rubbing over Derek's cheekbone as their eyes met again. Stiles' looked intense, contrasting his voice, and there was a sharp, curious light in them.

Derek ducked his head a little, smiling.

"That really makes you happy?" Stiles asked, and Derek tried to think. . . How to explain the wolfish desire to belong, the pleasure that shot through him at the casual claim Stiles' words asserted - offered. At the way Stiles had. . .

"You do. Make me. . ." Derek said, and Stiles blinked, pink creeping into his cheeks beneath his freckles. "But the wolf-" he broke off.

"I doubt you would have said that yesterday." Stiles said, self-deprecating. Derek growled at him, and he startled. "Derek?" he asked, maybe confused but not nervous.

"I do like you, Stiles." Derek said, shifting. "I mean- I have liked you, me saying that is not because of. . ." He hummed softly, glancing away.

Stiles stroked his cheek, giving him a lingering kiss. "Oh. That's. . ." he trailed off, huffing out a ragged breath, and his fingers curled, knuckles rubbing along Derek's jaw. "Me too, Derek." he said, nosing Derek's cheek, almost like a wolf himself. "What were you saying? What about your wolf?" Derek tensed a bit, and Stiles trailed light fingers over his jaw, making a coaxing noise.

"Makes the wolf happy," Derek said slowly, "being wanted - being owned. When it's . . . right."

'Owned' probably sounded wrong, particularly to human ears, it wasn't how-

Derek startled as Stiles hugged him tight, one hand petting the back of his head. His cheek pressed against Derek's, and Derek tightened his grip on Stiles again, surprised. Stiles rubbed their cheeks together gently, firm contact and . . . trusting. Open.

"So you'd like it," Stiles asked, leaning back, "if I called you mine?"

Derek squirmed a little, and Stiles grinned wickedly. "Stiles. . ."

"Mm, nice." Stiles stroked his cheek from brow to jawline. "You'll have to deal with it, big bad." he said playfully. "And. . . You have to howl for me." he added. "Please?"

Derek had to choke down the impulse to do it immediately, and quietly thought that he'd never have been able to resist giving in to the urge at some point no matter what Stiles asked. "Promise." he said, thinking how strange it was to have it asked of him to. . .

"And I'll drum for you." Stiles promised in return, cuddling into his chest, hand sliding down until curled fingers rested at the base of his throat. And Stiles asked him to be the wolf, to show it, and offered - promised - proof of Derek's song freely, and. . .

Derek swallowed against a thick feeling in his throat that had nothing to do with the impulse to howl. He clung to Stiles, having to remind himself, just a little, not to crush his soulmate enough to hurt him.

Hopefully it was clear in the story, but a heartsong is the voice (. . .or whatever it may be; there are some oddities out there) of your soulmate singing to you, which you hear in your dreams and recognise with an unmistakable feeling when heard in real life. (Kate took advantage of Derek's unusual heartsong to fake being his soulmate, lying that she heard his voice and refusing to 'prove' his own.)

(As I told my friend M when discussing this story . . . I managed to find one of the few ways I could make myself hate Kate even more. Without trying. Whoops.)