He was supremely happy, perched like an amorphous bundle on the high stool, with his head thrown back, his eyes fixed on the opposite cornice, and his lips wide open, sending forth, with all his might, impromptu syllables to a tune of Arne’s which had hit his fancy.
Excellent men, who had been forced all their lives to spell on an impromptu-phonetic system, and having carried on a successful business in spite of this disadvantage, had acquired money enough to give their sons a better start in life than they had had themselves, must necessarily take their chance as to the conscience and the competence of the schoolmaster whose circular fell in their way, and appeared to promise so much more than they would ever have thought of asking for, including…
There are no more uses of "impromptu" in the book.
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In one picture, which seems like the most recent but still looks a few years dated, his dad has his arms around the two boys, and he’s squeezing them together for an impromptu photo.
Colleen Hoover -- Slammed
I hesitate for a split second, long enough to place the tune—Frank Sinatra, "New York, New York"—and say a prayer of thanks that the Pugs aren’t witness to my mom’s impromptu performance.