You can see the sheet music for the above song at the web site of Baylor University, but I'm more interested in this parody:

You can play or download the following song at The Internet Archive. It's song #2 on that page. Here's my transcription:


RING DOWN THE CURTAIN, I CAN'T SING TO-NIGHT
Words and music by Lewis Ilda, Max Kester & Sonny Miller, 1936.
As sung by Gracie Fields, 1937

SPOKEN DIALOGUE:
—Oh, dear, dear, dear, dear! Oh, mister stage manager, please, I can't sing tonight!
—You can't sing tonight?
—No, I'm terribly sorry. I can't sing tonight.
—You must sing tonight! Your public's waiting!
—Oh, blow the public! It's impossible! I can't sing. I can't explain. I'm sorry.
—Go out an' knock 'em cold, baby. The show must go on!
—Oh, dear! Oh, dear! I can't!

SOPRANO, SINGING:
"Ring down the curtain. I can't sing tonight. Their money back you'll have to pay.
Ring down the curtain. I can't sing tonight. They've taken me false teeth away."

The theatre was packed from the pit to the stalls. The show was about to begin.
The baritone villain stood there in the wings. On his face was a dastardly grin.
The tenor had just finished padding his chest and was gracefully waving his hair.
The overture started. The curtain went up, when the heroine cried in despair:

"Oh, ring down the curtain! I can't sing tonight! Oh, dash it! I wish I was dead!
I can't sing tonight with me tonsils in sight. I haven't a tooth in me head!"

The manager said that the show must go on. He was in a terrible rage.
The baritone gave the soprano a push that shot her headfirst on the stage.
"You can't," cried the tenor. "Strike one your own size!" then leaped on the stage amid cheers.
He said, "What's the do?" because was his cue, and the heroine cried through her tears:

"Oh, ring down the curtain! I can't sing tonight!" She stood there and twiddled her thumbs.
The villain said, "Gnash me!" She said, "No, I can't! I can't gnash with only me gums!"

The heroine swooned on a velvet settee, but jumped up again with an "Ouch!"
Which rapidly turned to a cry of delight, for there were her teeth on the couch!
The lovers embraced as she slipped in her teeth. She turned with a smile on her face.
She opened her throat and let out a note that smashed ev'ry glass in the place.

(OPERATIC GIBBERISH FOLLOWED BY THE SOUND OF BREAKING GLASS.)

MALE CHORUS:
"Ring down the curtain. You can't sing tonight, or else you'll be put on the spot.
Some voices we've heard were a pain in the neck, but yours is the worst of the lot."

SOPRANO:
"Oh, ring up the curtain! I will sing tonight, in spite of your laughter and jeers.
If you're so upset by my beautiful voice, then put cotton wool in your ears!"

(SHRILL OPERATIC GIBBERISH FOLLOWED BY THE SOUND OF A GUNSHOT.)

MALE CHORUS: "You can't sing tonight."