Ruth Fielding at Briarwood Hall by Alice B. Emerson

In this, the second book of the Ruth Fielding series, Ruth goes to boarding school with her best friend Helen. When they get there, Ruth starts her own sorority called the SweetBriars for the new girls. Her sweet group of girls conflicts with the two other sororities the Upedes and the Fussy Curls. In the midst of settling in to the new place, there is a campus rumor about a legend of the marble harp playing ominously at night. But when the French teacher is in a fright, will Ruth be able to solve