Set-Switch Song

A Theatre trope. Basically a song to distract the audience while there is a scene or set change. Usually a blackout/whiteout is used for these but sometimes this does not give the crew enough time to move everything. The songs are rarely memorable or particularly plot-driving. Often similar to a Non Sequitur Scene in relevance to the overall plot but not in scale as that type of song usually requires a set and a big chorus of its own.

Examples of Set-Switch Song include:

"Dear Old Shiz" from Wicked.
"Boy for Sale" from Oliver!: Mr. Bumble and Oliver tend to walk downstage with the curtain down while the Workhouse Parlour set is taken out and the Undertaker's Shop is brought in.
"A Diva's Lament" (or "Whatever Happened to My Part"): from Spamalot. It doesn't even try to be relevant to the plot; the premise is that the actress is whining about her lack of involvement in early Act II, and the ridiculous plot elements that have cropped up that don't involve her. It also interrupts two scenes that are strongly related to one another. And, oddly, in many ways, it's a Crowning Music of Awesome.
"As Soon As I Get Home" from The Wiz in this troper's high school production was one of these. Our set for Munchkinland was pretty complex and involved a lot of heavy set pieces, and to be honest that song's not that fantastic anyway.
"Love Is Sweeping The Country" in Of Thee I Sing covers the transition from the Atlantic City scene to the Madison Square Garden scene, and wasn't even printed in the play's first published edition. It's a good song, though.
The Secret Garden has several of these, especially in the second act. Each of the groups of Dreamers gets a small bit, and even Dr. Craven gets a small solo. And the kicker is that the titles in the score include "-Transition."
They're usually singing Simlish in them, but many Cirque Du Soleil shows have songs and dances used solely for transitions between acts, especially if setpieces and/or equipment need to be moved on and/or off. Examples: "Egypte" and "Gambade" (Mystere), "Marelle" (Quidam), "Pokinoi"(Saltimbanco, after retiring the Vertical Rope), and "Africa" ("O").
"Frank Mills" in the musical Hair is a sweet little solo love song that's sole purpose is to allow the cast time to run backstage and change for the next set.
"I Sing Of Love" and "Brush Up Your Shakespeare" in Kiss Me, Kate. The published text even says the former song "gives us time to change to the next scene." Before the two gunmen sing the latter song, they try to figure out why they're in front of a safety curtain; they fail.
"Very Soft Shoes" from Once Upon a Mattress.
"On the Street Where You Live" from My Fair Lady covers the big set change from Ascot back to Henry Higgins' house.
"Her Is" from The Pajama Game does it twice, as the set is changed before and after the company picnic scene.
"The Highest Judge Of All" from Carousel.
"Open Up Your Mind" from the original TheatreWorks production of Vanities: The Musical, was sung by Mary to the audience during the Intermission, which was omitted from later productions.
In the Screen to Stage Adaptation of Aladdin, reprises of "Arabian Nights" are used for this.
Anything Goes, at least the original production, used "Bon Voyage" and "Sailor's Chantey" to cover set changes.
Pippin: Lampshaded in "Simple Joys" with the line "We all could use a change of scene."