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Listen boy
Don't want to see you let a good thing
Slip away
You know I don't like watching
Anybody make the same mistakes
I made

The Doctor watched his companion twirl about the music room in her short, flowing dress. It flared out around her as she danced to the music that floated through the air. It was an older song, not from her era, but he could tell that didn't bother her. Her eyes shut tight, her smile wide and innocent. He continued to lean against the frame of the door, hypnotized by her hair flying around her face, seeming to glow.

She's a real nice girl
And she's always there for you
But a nice girl wouldn't tell you what you should do

He thought back to how she had been with him for so long. Since his previous regeneration actually. She had helped him through so many things. Had saved his life so many times, he'd lost count. She was possibly the nicest and kindest companion he had ever had. Sweet and a bit shy, but ever curious about the universe. That's why he... Never mind.

Listen boy
I'm sure that you think you got it all
Under control

You don't want somebody telling you
The way to stay in someone's soul

You're a big boy now
You'll never let her go
But that's just the kind of thing
She ought to know

With the music tinkling in his subconscious, the Doctor continued to watch his companion sway and spin to the song. He didn't bother to hide his smile. He knew he shouldn't, but he felt his hearts swell as he stood there. He tried desperately to push down the feeling. He knew it was a terrible idea, but he found that the feeling had creeped up on him lately. Not really, that was a lie. It had been with him for a very long time, just like her, but he always managed to keep it at bay. Recently, though, the fluttery feelings had been happening closer and closer together. But it was fine. He was fine. He could hold it off. He had everything under control...
He couldn't ever let her know about it though, he couldn't live with the pain of losing her too. It seemed, every time he fell for someone, they were taken away from him. He couldn't have that. If one thing was for certain, it was that he would never let her go.

Tell her about it
Tell her everything you feel
Give her every reason to accept
That you're for real

Tell her about it
Tell her all your crazy dreams
Let her know you need her
Let her know how much she means

Listen boy
It's not automatically a certain guarantee
To insure yourself
You've got to provide communication constantly

When you love someone
You're always insecure
And there's only one good way
To reassure

Seeing her there, dancing as if no one was watching (though in her defense, that was exactly what she thought) it made him want to rush to her and wrap her in his arms, telling her over and over how much he loved her. How he has always loved her, and how he will never stop. But he couldn't. He was so scared. There were so many variables. So many outcomes where his hearts could be broken, or she might not want to travel with him anymore. He would hate himself if he lost such an amazing companion because he couldn't control his feelings.

Tell her about it
Let her know how much you care
When she can't be with you
Tell her you wish you were there
Tell her about it
Every day before you leave
Pay her some attention
Give her something to believe

Cause now and then
She'll get to worrying
Just because you haven't spoken
For so long
Though you may not have done anything
Will that be a consolation when she's gone

Listen boy
It's good information from a man
Who's made mistakes
Just a word or two that she gets from you
Could be the difference that it makes

She's a trusting soul
She's put her trust in you
But a girl like that won't tell you
What you should do

While the Doctor was worrying to himself, Y/N's spinning stopped abruptly when she noticed him at the doorway. Her hair and dress settled. A deep blush flooded her cheeks. Before she could question him, the Doctor smiled excitedly and said, "You know, I could take you to meet him, if you want." He rushed forward into the room, expecting her to agree and take off toward the control room. Instead, she replied, "Oh, no thank you." She looked around her, "I think the music room will be fine for now." The Doctor's face fell and she rushed to add, "Maybe another time though. I do like the song. I like quite a few of his songs actually, but this one in particular."
"Why is that," asked the Doctor, immediately perking up. He loved learning more about her. She smiled at his child-like curiosity. Then she thought for a moment and replied, "I guess I like wondering who he was writing it to. You know, what young man could he have been telling to confess his love to his sweetheart?" She looked at her feet and added quietly, "It's just something that has always interested me, I guess. The mystery of it, I mean." A light blush appeared on her face. The Doctor smiled at her embarrassment, finding it quite adorable. Then he realized what he was thinking and quickly shook it away.
As they stood there, the Doctor began to really listen to the song...

Tell her about it
Tell her everything you feel
Give her every reason
To accept that you're for real
Tell her about it
Tell her all your crazy dreams
Let her know you need her
Let her know how much she means

Suddenly, the Doctor took Y/N's hand. She looked up at him, startled, "D-doctor...? Wh-what are you-?"
"Y/N... I have to tell you something..." She continued to stare at him. All he could do was stare at her hand in his.
"What Doctor? Just say it." She said it gently, but it was still firm and compelling. Finally he couldn't hold it in any longer. He had to tell her about it...

Tell her about it
Tell her how you feel right now
Tell her about it
The girl don't want to wait too long
You got to tell her about it
Tell her now and you won't go wrong
You got to tell her about it
Before it gets too late

"Y/N, I-I... I love you."

The music room was silent except for the song still playing in the background. The Doctor was terrified that he had blown it. She wouldn't want to stay with him. She would want him to take her home. How could he be so stupid! So forward! He'd never even taken her on a date-!
"Doctor..." Her voice was a hardly audible whisper. He might not have even heard her at all if it weren't for the silence in the room already. He dragged his eyes from the floor, and stared into her beautiful (e/c) eyes that he loved so very much. She seemed speechless. Probably couldn't think of words to express how stupid he was being. He tried to drop her hand, but she tightened her grip. He gulped. He just wanted her to say something. Anything. He just needed her to tell him what she felt.
She stared so intently he thought he might combust or something, but finally she said, "I love you too, Doctor..." His eyes widened with disbelief. She blinked and stuttered, "I-I never thought it would be p-possible for you to feel the same. How could someone like you ever fall for someone like me. I'm just-" He never heard the rest of her ramblings. He quickly pressed his lips to hers. She stood shocked for a moment, but then she kissed back. His hearts swelled and his body felt like there was a new star exploding to life inside him. His hands moved to her face, and cupped her cheeks gently. He could feel her hands tangle in his hair behind his head. She deepened the kiss and his hearts started beating at rates he knew must be dangerous for his health, but he didn't care. It was better than he had ever dreamed.
Finally they broke apart. He knew he had the stupidest grin on his face, but it wouldn't go away, even if he tried. Y/N smiled too. Then he took her hand. As always, it fit perfectly in his.
Suddenly, Y/N spoke up, "You know Doctor, I think it's far past time for our next adventure." A thousand planets and times flew through his head, as he tried to decide on the perfect one to visit. Finally he did.
"You know, I think you're right Y/N. And I know just the place to go looking for adventures!" A twinkle appeared in her eyes, full of excitement and curiosity.
"Then what are we waiting for!" She dashed off toward the control room, leaving him in the dust. He casually walked over to the doorway. He looked back over his shoulder at the music room. The song was just ending, and the Doctor made a mental note. He'd have to thank the songwriter some time for the brilliant advice.
"Doctor! What's taking you so long!" Y/N yelled from down the hall. The Doctor shook out of his trance and shouted back, "Don't worry! I'm right behind you!" He heard her scoff and laugh from farther away. Her laugh filled him with happiness.
With a smile, the Doctor left the music room behind him, and he rushed off toward a brand new adventure.

In the soft, beautiful music room, the song finished:

You got to tell her about it
You know the girl don't want
To wait - you got to
Tell her about it