Author's Note: This is a one-shot, set in the world of The Life Of Sound (TLOS), which was my Winter 2015 Castle Ficathon story. I wanted to give you a glimpse of what's going on in the lives of this alternate Castle and Beckett a few months later. You can read this story if you haven't read TLOS, but I'm not sure how much sense it will make...

"Hey! Sorry I'm late," Kate Beckett gasped as she burst into her boyfriend's loft, cheeks flushed, eyes bright. "Hi Martha, Alexis." She dumped her purse on the side table by the entrance. "I had to take a phone call. You'll never believe the offer I just got."

"If it involved Robert Redford and a million dollars, I hope you said no," Rick Castle replied with a grin, coming out from behind the kitchen island with a salad bowl in his hands. He put the bowl on the dining table and came over to greet his girlfriend with a kiss. She rolled her eyes at him.

"You really need to update your pop-culture references, Castle."

"I keep telling him that," agreed his daughter, coming over to give Kate a hug. Martha wasn't far behind, offering Kate a quick squeeze and a glass of wine. With the ease of familiar routine, they all took their seats around the table.

"Anyway, no, there was nothing indecent about this proposal," Kate continued, practically bouncing in her chair with excitement. "I was invited to sing the national anthem at the Mets' season opener next week!"

Castle and his mother and daughter all exclaimed with delight. "That's awesome, Kate," Alexis gasped, wide-eyed as she passed the salad dressing. "It's such an honor."

"Yeah," Castle agreed, adding, "although of course it would be a bigger honor if it was the Yankees."

"Watch it, buster," Kate warned, glaring.

Alexis and Martha merely chuckled. The couple's team rivalry had become a running joke, increasing in frequency as the beginning of baseball season approached.

"I thought Roy said no more performing for a while, after the Magnificat last month?" Castle asked, more seriously.

Kate's eyebrows went up. "Well, yeah, but he can't say no to this, can he? I mean, it's just one song." She pursed her lips thoughtfully. "I'm sure he'll understand. He has to, because I need him to help me decide what key to do it in. Oh! And I have to figure out what to wear!"

"Ooh," Alexis put in, "you should wear that navy-blue dress with the little pearl buttons."

"Maybe. If I can find some shoes to go with it," Kate mused.

Castle was bemusedly wondering when his daughter had become so familiar with his girlfriend's wardrobe. But what came out of his mouth was: "So will you be able to get us tickets?"

"Richard," his mother chided, but Kate just grinned, nodding.

"Yeah, they said I can just let them know who I'm bringing, and - Oh my god, I have to call my dad!" She start to rise from her chair, then paused, looking at her watch, and sat down again. "Wait, he's still in London and it's past midnight there. I'll call him tomorrow." She looked over at Alexis. "You'll come too, won't you?"

"Of course. It'll be fun," Alexis replied happily. "I haven't been to opening day before."

"Martha?"

"Not my cup of tea, darling," the diva intoned with a fluttering of fingertips, "but I'll be cheering you on in spirit."

"With something stronger than a cup of tea in hand, no doubt," Kate teased, and both women laughed.

Castle found himself smiling as well, infected by Kate's excitement. And it always made his heart flutter to see her getting along so well with his mother and daughter.

Kate turned toward him then, saying, "But enough about me. How was everyone else's day?"

"Oh!" he exclaimed, remembering. "Well, my exciting correspondence of the day pales in comparison, but I did get an interesting letter. A high school in Boston is putting on a production of the second Derrick Storm opera, and the girl playing Clara Stryke wrote to thank me for writing such a juicy alto role." He faltered for a moment, his thoughts turning inward, but the three women were in the midst of reacting to his news and didn't seem to notice.

"That's so sweet," Kate was saying with a smile, reaching to serve herself a bread roll.

"Ah, yes, the appreciation of the younger generation is a lovely thing to see," Martha gushed, at which Alexis rolled her eyes, but then turned brightly toward her father.

"That's cool, though, Dad. You should write back and wish her luck and stuff."

"Actually," he said, perking up, "I was thinking, we haven't been to Boston for a while. I could fly up there and surprise them."

His mother and daughter shook their heads emphatically. "Richard, no," Martha chided, and Alexis added, "Dad, you can't do that. Remember what happened in Philly?"

"Oh, right," he sighed, deflating.

Kate looked from one to the other of them, curious. "What happened in Philly?"

"A few years ago, Richard got it into his head to show up unannounced at a college performance of the first Storm opera," Martha explained. "But he was recognized immediately, and it made the whole cast so nervous they could hardly perform, so to speak."

"The boy playing Derrick fainted backstage just before curtain," Alexis added. "It was ugly." Castle grimaced at the memory. Ugly was an understatement.

"Oh no," Kate winced. "Maybe not, then, babe. Especially if these are just high-schoolers. Way too much pressure."

"Okay, okay," he sighed. "I know, you're right. And I wouldn't want to steal their thunder, anyway."

"You could send them a card or something," Kate offered, and the other women nodded assent.

"That's a good idea." Castle cheered up again. "Maybe I'll arrange to have some pizza sent backstage after the show. Or a cake!" He rattled off onto that tangent, and the meal continued.

Kate hadn't missed the way Castle's expression had briefly dimmed when he mentioned the letter he'd received. She kept a covert eye on him throughout dinner, but he seemed fine, happily participating in the conversation.

When the meal was over and the dishes tidied away, dessert and postprandial coffee had been enjoyed, and the redheads had retreated to their own private spaces, Kate tugged her boyfriend over to the couch and sat them both down.

"So," she said, snuggling up to his side, pulling his arm around her, "are you going to tell me what's wrong?"

"Don't know what you mean," he replied defensively. His other hand came over to cup her cheek and turn her face toward him for a kiss. She curved into it willingly, savoring the taste of chocolate, coffee, and Castle, but pulled away after a moment.

"Come on, babe, something's bothering you. Is it me?" she asked hesitantly. "Did I do something?"

"No! No," he said emphatically, turning to face her fully. "You're amazing. Everything's great." He smiled, but it was unconvincing. Kate studied his face, trying to figure out what he was thinking, but he was unusually closed-off tonight.

"What is it then?" she prodded, because it wasn't in her nature to just let things go. "Is it the opera? Act Two is taking a lot longer to finish than Act One did."

"I've also been doing a lot of revisions on Act One," he answered, a little defensive again. "It'll be ready when it's ready."

"I wasn't trying to nag," Kate placated. "If you-" But Castle leaned in and kissed her again, then moved his mouth along her jaw, his hand rising to work at the top button of her shirt. Sweet tingles rushed across her skin everywhere he touched, leaving her breathless. She knew he was trying to distract her, but he was so incredibly good at it, damn him.

"It's fine," he muttered into her skin, pressing her back against the couch cushions, nibbling his way down her neck. "Everything's fine."

Kate tangled her fingers in his hair and willingly submitted to the enticements of his hands and mouth, until it reached the point where she had to insist that they move things to the bedroom.

But afterward, as they lay sprawled on his bed, sated, letting their heart rates come back down to normal, she resumed the conversation.

"Is there a problem with the opera, Rick?"

"Why would you say that?" he asked grouchily into the bedspread, his face buried in the crook of his arm. "It's coming along. I'm meeting with the publishers in a few days to talk about production plans."

"Is that what you're so worried about?" she asked, raising her eyebrows, although she knew he couldn't see. "That they won't like it, won't want to produce it?"

"Of course they'll like it," he scoffed. "It's awesome."

"Then what is it that's bothering you?" Kate persisted.

"Nothing. Everything's fine." He burrowed his face even further into his elbow.

"I don't believe you," she said baldly, rolling toward him, letting her hand fall on the broad bare expanse of his back. "Something's going on. Why won't you talk to me about it?"

She traced her fingertips lightly over the red marks her nails had just left on his back, blushing slightly at the sight. When she leaned over to press her lips to the small injuries, his body shuddered underneath her.

"I don't want to talk about the opera. Or anything," he said, muffled.

Castle sounded ridiculously petulant, so Kate decided not to push any more for tonight. She was still determined to figure out what he was upset about, but she could see that he wasn't going to say anything in this stubborn mood of his. She would try again tomorrow.

With that thought, she reluctantly hauled herself off of his bed and went into his luxurious bathroom.

In the shower, she sang some scales, which had become a habit since she'd resumed her singing lessons with Roy Montgomery a few months ago. There was just something about the way a voice resonated in the small, steamy space. It was a good way to keep the vocal muscles relaxed.

Then, experimentally, she sang: "O say, can you see, by the dawn's early light, what so proudly we hailed-" She could hear Castle entering the bathroom. "-at the twilight's last gleaming-" Then she skipped ahead. "And the rockets' red glare, the bombs bursting in air-"

Castle poked his head into the shower. "B-flat?" he said. "You could go higher."

She nodded and moved aside so that he could join her. "Yeah, maybe." She closed her eyes, tipping her head back to let the shampoo flow down her back.

"O say, can you see," she sang again, a whole step higher.

"Try D," Castle murmured, and she felt him looming beside her, reaching for the soap.

She went up another whole step. "O say, can you see, by the dawn's early light - And the rocket's red glare - That's too high," she said, opening her eyes, running her fingers through her hair to rinse out the last few suds.

"It's not too high. It's only up to A," Castle objected as she turned to face him. "Your A is glorious."

"I don't want it to get squeaky," she said, looping her arms around his neck. His hands drifted across her ribs and downward.

"It won't be squeaky," he vowed, a little breathlessly, pulling her body against his.

"No, it won't. If I'm doing it in B-flat," she said firmly. He dipped his head to nibble at her neck.

"Kate..."

She drew in a deep breath of the warm, steamy air. "And the rockets' red glare, the bombs bursting in air-"

"Something else is gonna burst," Castle murmured against her neck. She smirked and reached downward as he pressed her back against the shower wall.

"Better get it out of the air then."

Late the next morning, Castle knocked on Kate's apartment door. "Come in!" he heard her call, so he let himself in, juggling two coffee cups.

Kate was on the couch, holding her phone to her ear with one hand, rubbing her forehead with the other. "No, Yukiko. You can't give in to that," she was saying as Castle nudged the door shut with his foot. "Just tell him it isn't necessary. No, don't give him a choice. Are you kidding me?" She sighed, looking up to give Castle a grateful smile as he pressed a coffee cup into her hand.

"Listen, I gotta go, my lunch date's here," she said into the phone. "Yes. Yes, absolutely. Okay. Good luck."

She hung up and groaned, then took a long slow sip of the coffee.

"Perlmutter?" Castle guessed, plopping down on the couch next to her. She nodded and groaned again.

"He's a terror. Yukiko can handle him, I know she can, but she just needs to learn to stand up to him."

"Do you need to go over there, whip him into shape?" Castle suggested, rubbing her back lightly.

She shook her head. "No, that would just undermine her confidence even more. I need to leave her alone to work it out for herself."

"Sounds a bit like parenting." When Kate lifted her head from her coffee to look at his face, Castle turned serious. "You're not ... regretting your decision, are you?"

"To take a sabbatical from the orchestra? No," she said firmly. "It was the right choice for me. I need the time to work on my singing and figure out what I want to do."

Castle pursed his lips and carefully didn't ask the obvious follow-up question. But Kate could see it on his face anyway.

"I still don't know," she sighed, leaning against his shoulder. "I can't develop a singing career unless I give up the violin, and I'm still not sure if that's what I want."

"It's okay," he soothed. "You still have plenty of time to figure it out. There's no rush."

"It's been three months already!" she burst out, sitting up straight again in frustration. "By now I should at least have some idea of what I want to do." She took another gulp of her coffee, scowling.

"And people think I'm the impatient one in this relationship?" Castle quipped, grinning ruefully. She lifted her head and glared at him, which he blithely ignored as usual. "Kate, you dedicated yourself to violin for ten years. You closed yourself off from singing for a whole decade to protect yourself from the pain of your mother's death. You can't expect to get past all of that in just a few months. It's a process. It takes time."

"That's exactly what Roy says," she grumbled, setting down the coffee cup.

"Well, he's a very wise man."

She was still scowling, but Castle knew her moods by now, well enough to know that he could wrap an arm around her waist and bring her in against him without risking dismemberment. So he did, and she reluctantly allowed him to snuggle her, still grumbling under her breath.

"Are you ready to go to lunch?" he ventured.

"Yeah," she sighed, but then suddenly sharpened. "Wait. No."

"No?" he repeated, surprised, turning to look at her as she pulled away from him again. He quailed at the stern expression on her face.

"Castle," she began, and he suddenly knew what was coming. He sighed, grimacing as he put down his own cup.

"I said I didn't want to talk about it," he muttered toward his knees, perfectly well aware that he sounded like a pouting child.

"Yeah, you did, but that's too damn bad," Kate replied. Castle winced and squirmed a little in his seat at her tone.

"Okay. Look." He might as well just tell her, right? She was going to weasel it out of him eventually anyway. He sighed again and forced himself to look at Kate. The concern in her eyes made his chest feel tight with trepidation. He reached out to take her hands in his, smoothing his thumbs absently over the soft skin of the backs of her hands while he thought about what to say.

It had been bothering him for a while now, and he knew - had known all along - that he would have to tell Kate. But he couldn't bear the thought of what might happen if she didn't like what she heard.

"I'm meeting with my publisher the day after tomorrow about the opera," he began slowly.

Kate nodded. "Yeah?" she prompted, because she already knew this.

"And I, um." He paused, and groaned. Why was it so hard to find the right words? "I've been having a lot of trouble with that one aria, the opening number of Act Two."

"The one you had me sing some bits of a couple weeks ago," she put in, and he nodded agreement.

"Yeah. I've really been struggling with it, and it finally hit me what the problem was. It's in the wrong key."

Kate tilted her head to one side, frowning slightly in confusion. "So, you transpose it. Right?"

"Yeah." Here it was: the moment of truth. "But I would be transposing it down into alto range."

In the pause that followed, he lifted his eyes briefly from their entwined hands, sneaking a glance at Kate's face. She was staring at him expectantly, still not really getting it. He took a deep breath and continued.

"I realized that it's the same with all of Nikki's songs, basically. I'd been feeling all along that something wasn't quite right, and I finally see it - it's that they're all too high. Nikki wants to be an alto. I mean, she is an alto. It's what I've been missing this whole time."

"Okay," Kate said slowly, a small frown creasing her forehead. "Well, that would be a bit of a tonal shift, but that's okay, right? How long will it take you to transpose all the songs?"

"Not long. The software does most of the work," he answered, but now he was frowning too. "But ... you're not mad?"

"Why would I be mad?" she asked, truly confused.

He just stared at her, beginning to feel like a huge idiot.

Before he could figure out how to reply, light dawned in Kate's eyes. "Oh, Castle," she said, squeezing his fingers. "Did you ... were you thinking that I would sing Nikki? That you had to make her a soprano, for me?"

"Well, I." He looked down again, fidgeting, feeling his cheeks begin to flush red. "I mean, she is based on you, and you're a soprano."

"Yeah, but she's not me. You keep saying that yourself." Kate leaned toward him slightly, forcing him to look at her. "Rick. You didn't write the part for me to sing, did you?"

"No," he mumbled. "I know you're not ready to decide about pursuing a singing career at all, let alone commit to such a big project."

"Right," she nodded.

"And even if you were, it would be way too meta."

Kate's brow furrowed slightly, and he saw her mouthing the word meta to herself, bemused.

"But I just thought, I don't know," he sighed, "I guess I wanted to leave the option open. In case someday you do decide that you want to do it."

She studied his face for a long moment. "Well," she said at last, surprisingly lightly, "if I do, you'll just have to transpose all the songs back up for me."

A surprised laugh burst out of him, and he felt a sudden intense surge of relief at the way Kate's eyes were twinkling. He had really been fretting over nothing all this time. It was all going to be okay.

"I will," he vowed, "of course I will."

"But babe, you have to write it the way you want to write it," she added, more seriously. "Not constrain yourself by what you think I might want. Or anyone."

"I know, I know." He bobbed his head up and down in agreement. "You're right, of course." How was she so sensible? How was he so lucky?

"Is this really what you've been so worried about these past few days?" Kate asked, untangling one hand from his, lifting it to his face. Her fingers brushed lightly across his forehead, smoothing his hair back, caressing his temple. "Stressing yourself out over how I'd react to Nikki being an alto?"

"I'm such an idiot," he groaned, closing his eyes and leaning his face into her palm. She huffed in denial, her fingers still lightly stroking his skin.

"No you're not. I think it's sweet."

"Really?" His eyes popped open, and his chest tightened deliciously when he saw the tenderness and affection in Kate's gaze.

"Really." She nodded, biting her lip. "This is your creation, your work. You've been so consumed by it these past few months, and to think that you still manage to think about me and my feelings at the same time..." She ducked her head, suddenly timid. "It's pretty amazing."

"Of course I think about the woman I love. How could I not?" he said in surprise.

He saw her eyes widen, felt the gentle movement of her hand on his temple suddenly go still. His breath caught in his throat as he realized with a jolt that it was the first time he had said that to her.

When he first met Kate Beckett, she had seemed so closed off. But as he got to know her, he had realized how much passion and fire was hiding behind her guarded eyes. It had just been so very long since she had let anyone in.

Rick Castle, on the other hand, was a heart-on-his-sleeve kind of guy. He had said those three little words before, but when he thought about Kate Beckett, he knew that he had never felt this way about a woman before. Not even the one he had married. So it surprised him to realize that he hadn't told her yet.

All of this flashed through his mind in a heartbeat as he watched her react, and just like that, his self-confidence was back.

"Kate," he said softly, smoothly. He reached up and took her hand, moving it from his forehead to his mouth, pressing his lips to it in a light kiss. "I love you. You must know that."

She lifted her eyes to his face, tentative.

"And not just because you're my muse," he added. To his enormous relief, her expression lightened at the joke.

"I told you not to call me that," she snipped, but the hint of a smile at the corners of her mouth gave her away. He smirked in response and leaned toward her, still holding her hand in one of his. He lifted his other hand to cup her cheek and softly pressed his lips to hers.

"I love you too," she whispered into the kiss.

Castle felt his breath stutter in his throat again, shock rushing through him. But before he could fully react, she pulled him into another kiss, this one deeper and darker than the one before. Her tongue stroked into his mouth as if it owned the place - which of course it did, he thought dizzily - and her fingers dug into his shoulders, tugging him closer.

"Kate," he gasped into her mouth, shuddering pleasurably as her hands crept under his shirt and slid along his skin. "I thought we were going to get lunch."

"Lunch can wait," she husked. She pushed him back against the couch cushions, straddled his lap, and pressed herself against him.

"O say does that star-spangled banner yet wave..." sang Kate, and the crowd of forty thousand people began to cheer.

"O'er the land of the free..." Her voice sailed effortlessly up to the high B-flat, and the cheers rose, becoming so loud that the final phrase was nearly drowned out by the noise.

"And the home of the brave?"

The crowd stomped and cheered with enthusiasm, none more so than the four fans in section 114, row 3. Alexis was bouncing up and down in her excitement; Castle couldn't help letting out a whoop; and Roy Montgomery put two fingers in his mouth to produce an ear-splitting whistle. Jim Beckett merely stood, grinning from ear to ear and applauding fiercely.

Kate was smiling too as she waved to the crowd, soaking in their approval. The sight of her little fan club warmed her; any butterflies she might have felt when she first stepped out onto the dirt had long since flown away. Her eyes sought out the tall bulk of her boyfriend, and she couldn't stop smiling as the stadium security guard escorted her off the field.

She still didn't know what the future held for her: professionally, musically, or even personally. But each time she stood up in public and let her voice ring out, she felt her heart heal a little more, and she felt closer to her mom than ever before.

"Play ball!" called the announcer, and the crowd cheered again as the Mets took the field, but Kate only had eyes for Castle. She made her way up the aisle to where he and the others stood, still clapping.

Her mentor, her dad, and Castle's daughter were all beaming and clamoring at her, and she was eager to accept their hugs and congratulations. But before any of that, she was drawn like a magnet to her boyfriend, who wrapped her in a bear hug so strong it lifted her off her feet with a startled squeak.

"Hey, you were right," he said into her ear, squeezing her tightly, her arms locked around his neck. "B-flat was perfect."

She laughed delightedly, intoxicated by the rush of a successful performance, the energy of the crowd, the heady rush of her feelings for this amazing man. "Yeah," she agreed, tossing back her head to grin into his eyes. "It was."

He dipped his head to kiss her soundly. "I love you," he whispered, for her ears only, just the two of them alone together at the center of the roaring crowd. She breathed in and out contentedly and kissed him again.

"And I love you," she whispered back. "Now let's watch the game."