From 1919 onwards, Hindemith began to trust his compositional talent and also to regard himself as a composer. This new self-conception released an unparalleled productive energy in him. In 1919-1921, alongside numerous entertainment works, parody pieces and the extensive film music Im Kampf mit dem Berg, he composed a solo sonata, two duo sonatas, two string quartets, two lieder cycles, a lied collection, two piano suites, a piano sonata, three one-act operas and the Rag Time (well-tempered). In these works he freed himself from the "late-romantic" expressive world of his early works, developing his own form of expressionism in close connection with contemporary poetry.
The 2nd String Quartet, Op. 10 and the Six Sonatas, Op. 11 are the works in which Hindemith finds a new stylistic orientation. He himself confirmed this by notating on the sketches for the Sonata for Violoncello and Piano, Op. 11 No. 3: «A transformation is taking place here!»
If the influences of Brahms, Strauss, Debussy, Reger and Busoni are still noticeable in these works, all outside influences have been overcome in the piano pieces In einer Nacht op. 15 and in the 3rd and 4th String Quartets, Op. 16 and Op. 22. In these works, Hindemith's expressionism is not so much to be understood as a completely unconnected, free self-expression of the composer; it reveals a growing confidence in the purely musical expressive power of the most multifarious musical material imaginable, taken up from all domains. One finds in these works parody, entertainment, complexity, playfulness, strong expression, simplicity, the grotesque, inexpressive qualities and terseness all at once, held together by the vital élan of music making.