Final answer:
The first period of music composition was the Classical period, which focused on defined musical structures and clarity. As the Romantic period later emerged, expressive depth in composition became more prevalent. The turn of the century saw composers seeking innovation through nationalistic music and avant-garde techniques.
Step-by-step explanation:
The first period in music composition, often referred to as the Classical period, exhibited unique signs such as an emphasis on classical forms and structures. Composers in the eighteenth century were primarily interested in clear and identifiable musical forms, harmonies, and melodies. They sought to create music with an easily audible structure, differing from the later Romantic period which would explore more expressive realms and emotional depths.
As music progressed into the post-Romantic era at the end of the nineteenth century, there was a shift in compositional style. Composers began to concentrate on the traditions of their own countries, leading to a proliferation of strongly nationalistic music. Others, like Mahler and Strauss, pushed the boundaries of Romantic techniques. By the end of the century, the turn away from Romanticism spurred the search for new idioms, which led to Impressionism and early Modern music.
Early twentieth-century art movements reflected the chaotic world at that time and its influence on music was similarly transformative. Musicians experimented with new scales, notes, and tempos, radically altering the listening experience with avant-garde techniques. This quest for innovation indicated a departure not only from classical norms but also from established Romantic conventions.