It has continued to be influential through the subsequent history of classical music through to the modern period. The 20th century brought a wealth of scholarship that sought to found the theory of the sonata form on basic tonal laws. The 20th century would see a continued expansion of acceptable practice, leading to the formulation of ideas by which there existed a "sonata principle" or "sonata idea" that unified works of the type, even if they did not explicitly meet the demands of the normative description.