Baroque music, as well as the popular art and architecture of the Baroque period, puts an emphasis on adornment. Immediately following the Renaissance, Baroque composers were the first to establish multiple instrumentation and use complex harmonies in their compositions. Baroque music favored the harpsichord and other stringed instruments, while the Classical period preferred the piano, brass and woodwinds. Baroque music also allowed for much more improvisation than Classical music and featured many more opportunities for ensemble soloing. Baroque composers were also the first to establish opera as a musical genre.
Classical music is generally considered to have begun with the invention of the sonata. Early Classical music was among the first to express two different moods by using sonatas--one more lyrical and one more fast-paced--while Baroque music, and its predecessors composed only one mood per movement. The Classical era also saw the emphasis on the piano as the main instrument used for performing compositions. Classical composers are governed by many rules of structure, most notably the evolution of the rondo style ABA or ABACA, as opposed to the most common Baroque rondo style of ABACABA.
Baroque music predates Classical, though towards the end of the Baroque period there is a bit of an overlap as it evolved into the Classical period. It is generally agreed that the Baroque period began after the Renaissance in approximately 1600. Baroque style was the dominant force in European music, art and architecture until 1750, when Classical music gained popularity. Classical composers then dominated the Western musical tradition until the beginning the Romantic era at the beginning of the 19th century.
The most famous composers of the Baroque era include Bach, Vivaldi, Monteverdi, Handel and Corelli. Vivaldi, a student of Corelli's, was a popular composer of the late Baroque period, and among the first to canonize the characteristics of Baroque music, including the use of the rondo. The Classical era was considered to be ushered in by the compositions of Haydn as he was one of the first composers to develop piano trios and the sonata form, both of which distinguish Classical music from Baroque. Other famous Classical composers include Schubert, Beethoven and Mozart.