section_path: History/20th and 21st century
section_name: 20th and 21st century
paragraph_text: 20th and 21st century
  
  In the 19th century, a key way new compositions became known to the public was by the sales of sheet music, which middle class amateur music lovers would perform at home, on their piano or other common instruments, such as the violin. With 20th-century music, the invention of new electric technologies such as radio broadcasting and mass market availability of gramophone records meant sound recordings heard by listeners (on the radio or record player) became the main way to learn about new songs and pieces. There was a vast increase in music listening as the radio gained popularity and phonographs were used to replay and distribute music; anyone with a radio or record player could hear operas, symphonies and big bands in their own living room. During the 19th century, the focus on sheet music had restricted access to new music to middle and upper-class people who could read music and who owned pianos and other instruments. Radios and record players allowed lower-income people, who could not afford an opera or symphony concert ticket, to hear this music. As well, people could hear music from different parts of the country, or even different parts of the world, even if they could not afford to travel to these locations. This helped to spread musical styles.
  
  The focus of art music in the 20th century was characterized by exploration of new rhythms, styles, and sounds. The horrors of World War I influenced many of the arts, including music, and composers began exploring darker, harsher sounds. Traditional music styles such as jazz and folk music were used by composers as a source of ideas for classical music. Igor Stravinsky, Arnold Schoenberg, and John Cage were influential composers in 20th-century art music. The invention of sound recording and the ability to edit music gave rise to new subgenres of classical music, including the acousmatic and Musique concrète schools of electronic composition. Sound recording was a major influence on the development of popular music genres, because it enabled recordings of songs and bands to be widely distributed. The introduction of the multitrack recording system had a major influence on rock music, because it could do more than record a band's performance. Using a multitrack system, a band and their music producer could overdub many layers of instrument tracks and vocals, creating new sounds that would not be possible in a live performance.
  
  Jazz evolved and became an important genre of music over the course of the 20th century, and during the second half, rock music did the same. Jazz is an American musical artform that originated in the beginning of the 20th century, in African American communities in the Southern United States from a confluence of African and European music traditions. The style's West African pedigree is evident in its use of blue notes, improvisation, polyrhythms, syncopation, and the swung note.
  
  Rock music is a genre of popular music that developed in the 1950s from rock and roll, rockabilly, blues, and country music. The sound of rock often revolves around the electric or acoustic guitar, and it uses a strong back beat laid down by a rhythm section. Along with the guitar or keyboards, saxophone and blues-style harmonica are used as soloing instruments. In its "purest form", it "has three chords, a strong, insistent back beat, and a catchy melody." The traditional rhythm section for popular music is rhythm guitar, electric bass guitar, drums. Some bands have keyboard instruments such as organ, piano, or, since the 1970s, analog synthesizers. In the 1980s, pop musicians began using digital synthesizers, such as the DX-7 synthesizer, electronic drum machines such as the TR-808 and synth bass devices (such as the TB-303) or synth bass keyboards. In the 1990s, an increasingly large range of computerized hardware musical devices and instruments and software (e.g. digital audio workstations) were used. In the 2020s, soft synths and computer music apps make it possible for bedroom producers to create and record types of music, such as electronic dance music, in their home, adding sampled and digital instruments and editing the recording digitally. In the 1990s, bands in genres such as nu metal began including DJs in their bands. DJs create music by manipulating recorded music, using a DJ mixer.