Sound recording was also a major influence on the development of popular music genres, because it enabled recordings of songs and bands to be inexpensively and widely distributed nationwide or even, for some artists, worldwide. The development of relatively inexpensive reproduction of music via a succession of formats including vinyl records, compact cassettes, compact discs (introduced in 1983) and, by the mid-1990s, digital audio recordings, and the transmission or broadcast of audio recordings of music performances on radio, of video recordings or live performances on television, and by the 1990s, of audio and video recordings via the Internet, using file sharing of digital audio recordings, gave individuals from a wide range of socioeconomic classes access to a diverse selection of high-quality music performances by artists from around the world. The introduction of multitrack recording in 1955 and the use of mixing had a major influence on pop and rock music, because it enabled record producers to mix and overdub many layers of instrument tracks and vocals, creating new sounds that would not be possible in a live performance. The development of sound recording and audio engineering technologies and the ability to edit these recordings gave rise to new subgenres of classical music, including the Musique concrète (1949) and acousmatic (1955) schools of electronic composition.