"to which the present daughters of the house were gradually giving the proper air of confusion by a grand piano forte and a harp, flower-stands and little tables placed in every direction."

Accomplished young ladies in the Regency period were expected to excel at music, specifically the piano forte (or fortepiano).

Pianoforte and harp
Creative Commons Attribution Share AlikePianoforte and harp - Credit: Thesupermat

While this picture depicts a far grander salon (Le Petit Trianon), the Musgroves would have been able to afford very good instruments and the character of Louisa suggests she would have demanded them.

Fortepiano 1805
Creative Commons Attribution Share AlikeFortepiano 1805 - Credit: Paul McNulty, Viviana Sofronitzki

The sound quality differed on the piano forte, an early version of a piano.  The octave range also was smaller.

Here is an example of an early 19th century song for the piano such as the misses Musgrove might have learned to play: