Best PRE-intro to a musical?

I'm looking for some help from the musical gurus on this forum.

Generally musicals will have some INTRO to the story being told -- often a song that provides the setting (e.g., Downtown, Dear Ole Shiz, Heat is on in Saigon, Good Morning Baltimore, etc., etc.).

But very often, BEFORE the intro, there is some PRE-intro; sometimes it is someone in the future who is letting us know they are going to tell us the story of what happened. E.g., Narrator starts off Little Shop ("On the 23rd of September, in a year..."), Galinda starts in the future and tells the story of the wicked witch, Phantom starts in the future with the auction, Adam in the future starts American in Paris and tells us the story.

Can you think of any other really good PRE-intros to musicals?

Would the vocal overture and night waltz from A LITTLE NIGHT MUSIC count?

Is it possible you are looking for the phrase "opening number"?

"Is it possible you are looking for the phrase "opening number"?"

Or Prologue?

Great responses so far. And no, as my introductory post explains, opening number would not be accurate. It is usually what happens before the opening number. Kad and Lyls, you got it!

I never saw Sunset Blvd (I only know the music). Is that how the staged version opened with Joe Gillis floating dead in the pool? That is cool. These are exactly the types of examples I'm looking for.

What you're actually looking for is called a framing device.

The new version of Carrie starts with detectives interrogating Sue about what happened at the prom.

Catch Me If You Can starts with Frank being captured by the FBI, and tells his story then.

Fun Home is narrated throughout by 43-year old Alison, while the plot shows 9- and 18-year old Alison.

Most of A Gentleman's Guide to Love and Murder is Monty writing his memoirs in prison.

Love Story starts with the protagonist's funeral.

Bare: The Musical (not the Pop Opera, though) starts with Peter talking at Jason's funeral.

Yank! starts with someone finding the protagonist's journal in a junk shop.

Updated On: 5/19/15 at 04:20 PM

How about the narrator of Damn Yankees….who narrates a bit before "Six Months Out of Every Year" goes into full swing. He starts out with "Good evening…." It's kind of part of the song, as the guys and their wives on stage are reacting to what he's saying. But it's not sung.

That is a great opening number, by the way.

Would the opening of GREY GARDENS count? They show the tabloids with the voice over and you get a glimpse of little Edie's eyes in the window before the reveal of the act one version of the home. Very effective.