The fusion of historical and emergent styles, forms, techniques, and content in a given work is encountered with great frequency in the music of most periods. The fugue, for example, whose origins can be traced to the imitative counterpoint of the late Middle Ages and which reached full maturity in the works of Johann Sebastian Bach, figures prominently in the musical styles of a number of important composers in the 19th century and beyond, including Beethoven, Mendelssohn (whose early works were modelled on symphonies of C. P. E. Bach), Reger (whose works for solo cello, viola or violin closely imitate Bachian forms), Shostakovich, and Hindemith.