I have to add a page for Haydn, the master of so many forms of music. Currently listening to his ‘Farewell’ symphony which was written as a musical prod to his employer that he and his orchestra would like to go home after a long tour. The last movement of five led to one member getting up and leaving the performance every so many bars until just Haydn and his senior violinist remained. It worked!
Hugely respected composer and pushed music into the classical period especially with a re-enhancement of sonata form. This laid the way for later composers such as Beethoven to push the boundaries even more.