She was taken aback by the suggestion that she was expected to show herself accomplished in music.

Evidently she must consult the duke.
She and the Lump and Miss Belthorp lunched with him, or rather they dined and he lunched.

After it, having seen the Lump safely on his way upstairs with Miss Belthorp, Pollyooly followed the duke into the smoking-room.
"Please, your Grace: Miss Belthorp seems to expect me to know how to play the piano; and I don't know how to at all," she said gravely.
"The deuce you don't!" said the duke.

"Here's another thing I never thought of." "I don't _mind_ learning the piano," said Pollyooly with a sigh.
"Yes; but if you showed that you didn't know anything about it, it would look very suspicious indeed," said the duke; and he frowned deeply as he cudgelled his brains for a way out of this unexpected difficulty.
"I expect it would," said Pollyooly.
He frowned on, fidgeting; then he said with decision: "Well, the only thing to do is to stop it altogether." "That would be quite safe," said Pollyooly brightening.
"All right: I'll see to it," said the duke.
Pollyooly left him with her heart at ease.
He frowned over the matter for some time, for it did not seem to him to be quite in the natural order of things that a duke should actually refuse to allow his daughter to learn the piano.

But he could find no other way of concealing Pollyooly's damning ignorance of the art of music.
At last therefore he sent for Miss Belthorp and said: "I--er--have decided that--er--Poll--er--Lady Marion is not to learn the piano." "Not learn the piano ?" said Miss Belthorp in the tone of one afflicted with the last amazement.
"I--er--have never observed the--er--slightest aptitude in her for it," said the duke with perfect truthfulness.
Miss Belthorp blinked.