Final answer:
The United States, Germany, and Russia were significant countries/cultures during the 20th-century music time period.
Step-by-step explanation:
The 20th century was a time of significant musical innovation and experimentation, with a variety of countries and cultures making notable contributions. Some of the most prevalent and relevant countries during this time period were:
- United States: Known for genres such as jazz, blues, and rock 'n' roll, the United States had a major influence on popular music worldwide.
- Germany: Home to the groundbreaking works of composers such as Arnold Schoenberg and the development of atonal and twelve-tone music.
- Russia: Boasted influential composers like Igor Stravinsky and Sergei Prokofiev, who experimented with new musical forms.
These countries/cultures were significant in shaping the musical landscape of the 20th century and their contributions continue to resonate today.