The practice of the Classical period would become decisive for the sonata; the term moved from being one of many terms indicating genres or forms, to designating the fundamental form of organization for large-scale works. This evolution stretched over fifty years. The term came to apply both to the structure of individual movements (see Sonata form and History of sonata form) and to the layout of the movements in a multi-movement work. In the transition to the Classical period there were several names given to multimovement works, including divertimento, serenade, and partita, many of which are now regarded effectively as sonatas. The usage of "sonata" as the standard term for such works began somewhere in the 1770s. Haydn labels his first piano sonata as such in 1771, after which the term "divertimento" is used sparingly in his output. The term "sonata" was increasingly applied to either a work for keyboard alone (see piano sonata), or for keyboard and one other instrument, often the violin or cello. It was less and less frequently applied to works with more than two instrumentalists; for example, piano trios were not often labelled "sonata for piano, violin, and cello."