The Talking Table Mystery by Georgess McHargue, 1977.
Annie Conway and her friend How are helping her great aunt to clear out her basement when they find a table that How thinks would work for his pet guinea pig’s cage. However, it’s not an ordinary table. It makes strange noises whenever they press on it, and in the box tied to the top of the table, they find a strange assortment of objects, including a little silver piccolo and some diaries.
Most of the diaries belong to Annie’s great grandfather, but there is one written by an unknown young girl. The girl apparently stayed in Annie’s great grandfather’s house years ago, and her diary refers to the girl’s mother’s strange behavior and the girl’s fears that something bad will happen. The diary itself is mysterious, but soon the kids start receiving threatening notes, telling them to hand over the diaries or something bad will happen. Who wants the diaries and why?
The basis for the mystery is 19th century spiritualism. The former owner of the table was a spiritualist who used it for seances, creating rapping noises when the “spirits” were present. As for what eventually happened to the girl and her mother, the clues are contained in the diary and with the people who now want them.