In the early 19th century, the sonata form was defined, from a combination of previous practice and the works of important Classical composers, particularly Haydn, Mozart, Beethoven, but composers such as Clementi also. It is during this period that the differences between the three- and the four-movement layouts became a subject of commentary, with emphasis on the concerto being laid out in three movements, and the symphony in four. Ernest Newman wrote in the essay "Brahms and the Serpent":

That, perhaps, will be the ideal of the instrumental music of the future; the way to it, indeed, seems at last to be opening out before modern composers in proportion as they discard the last tiresome vestiges of sonata form. This, from being what it was originally, the natural mode of expression of a certain eighteenth century way of thinking in music, became in the nineteenth century a drag upon both individual thinking and the free unfolding of the inner vital force of an idea, and is now simply a shop device by which a bad composer may persuade himself and the innocent reader of textbooks that he is a good one. After the Romantic period
The role of the sonata as an extremely important form of extended musical argument would inspire composers such as Hindemith, Prokofiev, Shostakovich, Tailleferre, Ustvolskaya, and Williams to compose in sonata form, and works with traditional sonata structures continue to be composed and performed.
A dance movement, frequently Minuet and trio or—especially later in the classical period—a Scherzo and trio. A finale in faster tempo, often in a sonata–rondo form.When movements appeared out of this order they would be described as "reversed", such as the scherzo coming before the slow movement in Beethovens 9th Symphony. This usage would be noted by critics in the early 19th century, and it was codified into teaching soon thereafter. It is difficult to overstate the importance of Beethovens output of sonatas: 32 piano sonatas, plus sonatas for cello and piano or violin and piano, forming a large body of music that would over time increasingly be thought essential for any serious instrumentalist to master. Romantic period
In the early 19th century, the current usage of the term sonata was established, both as regards form per se, and in the sense that a fully elaborated sonata serves as a norm for concert music in general, which other forms are seen in relation to. From this point forward, the word sonata in music theory labels as much the abstract musical form as particular works. Hence there are references to a symphony as a sonata for orchestra. This is referred to by William Newman as the sonata idea. Among works expressly labeled sonata for the piano, there are the three of Frédéric Chopin, those of Felix Mendelssohn, the three of Robert Schumann, Franz Liszts Sonata in B minor, and later the sonatas of Johannes Brahms and Sergei Rachmaninoff.