Those who might think that Broadway musicals are created when the playwright writes the script, then the composer and lyricist sit in a room and write all the songs (in order), and then the director casts and rehearses the actors, and the curtain goes up — would be well advised to read Hamilton: the Revolution (or any book about the genesis of a similar phenomenon, like this one or this one.)
Again, we call this this King of Hearts Fallacy, from the instructions given by that hapless soul during the trial in Alice in Wonderland: `Begin at the beginning,' the King said gravely, `and go on till you come to the end: then stop.'
This is not how artists create, and there has never been a Broadway musical, hit or flop, Hamilton or Carrie, that was created straight through from overture to finale. That's just not the way it works.
It doesn't work that way for any artist: poet, novelist, painter, sculptor, gardener, cocktail craftsman.
This is important to realize because many citizen artists — those of us who are not Lin-Manuel Miranda — think that's the way they have to do it, and since they cannot see past that brilliant first chapter or verse or sketch, they never get to the second.
Don't let this happen to you. Start at the end. Start in the middle. Start with the big scene. Or start at the beginning, and when you get stuck, skip to the next part you know. Just get it started, and then keep adding to it.
Each SUCCESSIVE APPROXIMATION will give you the chance to add to it, to correct what you've already done, and to start connecting all the dots. Or linking all the chains. Or whatever metaphor you want to choose.
Here's a metaphor: build your building blocks, then build your castle.