Throughout his life, Beethoven liked to keep his unpublished manuscripts and old sketchbooks by him, including chamber music which he had composed in Bonn or during his early years in Vienna; from time to time, he borrowed ideas from them. Although some manuscripts were lost, a few complete and incomplete compositions were discovered after his death and published posthumously. Among them was a sedate teenage Allegretto in E flat major, Hess 48, for piano trio, composed in Bonn in 1784, and three piano quartets, WoO 36, composed the following year. Beethoven may have sensed that, like a boy's newly broken voice, his ambitious and experimental piano quartets were too raw for wider circulation, but he made good use of them in some of his later music. The opening bars of the slow movement in the Piano Sonata in F minor, op. 2 no. 1, for instance, are almost the same as the opening bars of the slow movement in the third piano quartet and share its expressive mood. Less experimental, though more appealing and ‘presentable’ was the graceful Piano Trio in E flat major, WoO 38, composed in Bonn in 1790–1, in which Beethoven proved to himself that he could speak the polite and civilized musical language of his contemporaries to perfection, before embarking on what he would later describe as his ‘more important works’.