In the 19th century, music was part of the educational canon of the middle classes, alongside a humanist education, proficiency in several languages, and knowledge of literature, art, and theatre. Domestic music-making in particular reached its height during the Biedermeier period: daughters from the upper European middle classes took piano and singing lessons. Skills in this area increased the chances of a successful marriage. The square piano was less expensive than a grand piano and, because of its more intimate sound, especially popular for making music at home. As a domestic instrument, it became increasingly popular among the middle classes.