The Forums (David and Polly, and the children Myra, Sebastian, Wolfgang and Ethel) live in a house called Apple Bough, and are a very musical family. David is a pianist, and considered one of the best accompanists in the country. Polly had been training to be a professional singer before her marriage: after her marriage she gave up training, and became an artist.

All of the children can play the piano nicely, but Myra, Wolfgang and Ethel are "born amateurs". Sebastian plays remarkably well, but there seems to be something missing. However, when he is four David and Polly realise that the violin is his instrument, and he begins taking lessons, and practising up to four hours a day. Because of his violin lessons, Sebastian cannot go to a normal school, so David and Polly engage a governess to teach all the children - Miss Popple, who soon becomes known as Popps.