What do you mean, Rufnek, about the sitting in an empty theatre in your dreams? Does it actually feel like you're in a theatre watching your dreams - can you see this theatre?
It's more the feeling I'm in a theater at a live performance--I mean, I don't look around at other members of the audience nor am I aware of someone sitting in front, beside, or behind me, and I don't go out for a drink or pee during intermission. It's more like an empty theater in that I know I'm THE spectator, whatever is being performed is for my benefit. And it's definitely live theater in that it's happening as I see it. The performers are real, not remote as in a movie or on TV. I can go up on the stage and walk among them if I want, but they are not threatening and cannot come in contact with me so that some separation between performers and audience is maintained.
It's not always a theater setting. In a nap a few moments ago, I was with my children back when they were children but at the 50th reunion of my high school graduating class that is scheduled at the end of this month. I was telling them some sea-story about one of my youthful adventures when I noticed a guy leaning against the wall across the room, a fellow with whom I went to high school. I excused myself from my kids, walked over to my former classmate and told him as we shook hands that he had changed the least of all the people I had seen at the reunion. Didn't matter I didn't recall seeing anyone else at that moment or that he looked exactly like he did in high school--hadn't aged at all. It was like a combination of actually seeing and talking to him and at the same time seeing and hearing me interact with him. (Later in that dream I did encounter other classmates who also had aged very little, as had I--they were all female and I kissed and hugged them all like we were still in our teens.)
Also, like a theater, some sets will reappear in my dreams--an old house sitting damaged on a muddy European battlefield in one dream may be recyled as a well-kept Kansas farmhouse in another. A large air termnial through which I and others are wandering may be recognizeable as a massive warehouse (think the final scene of Raiders of the Lost Ark) in another.
Sometimes I get involved in a search or a trip in which there are unanswered puzzles to solve, but mostly it's more like watching a play by other performers unfold.
As for songs, I usually awake each morning with some song running through my head, something I'll sing in the shower and hum through the rest of the day. Not necessarily related to a dream--just my "song du jour." Occasionally my dream-in-the-empty-theater is a musical filled with lovely songs with witty lyrics and involving chorus lines of dancers, with me thinking at the time, "I gotta remember to tell my wife about this when I wake up!"
As for waking laughing, I've even come out of anesthesia laughing. I've also awaken from dreams talking and, occasionally, crying. On rare occasions, I've awakened fighting, just punhing hell out of a pillow or mattress; once I even clipped my sleeping wife.
Odd thing--I've never ever sleepwalked, not once; yet I dream almost nightly, sometimes several times a night, and generally remember the gist of what I dreamed sometimes in minute detail.
My wife, on the other hand, did sleepwalk as child, often to the point of going outdoors. Yet she rarely dreams and doesn't remember much about it when she does. She of course is much more practical and mature than I am.