Chopin's Piano Sonata No.1 in C minor, Op.4, composed at age 18, reflects his early experimentation with large-scale forms. Though less popular than his later sonatas, it showcases his emerging Romantic style within classical sonata traditions.
Chopin's least-recorded sonata, written at age 18, experiments with irregular meter (5/4 in third movement) while showing influences from Hummel and Weber. Its structural freedom contrasts with his later sonatas.