series of memorial concerts, selling his manuscripts, and collaborating with her second husband, Georg Nissen, on a biography of Mozart. In the 19th century, sheet-music publishers dominated the music industry. Before the invention of sound recording technologies, the main way for music lovers to hear new symphonies and opera arias (songs) was to buy the sheet music (often arranged for piano or for a small chamber music group) and perform the music in a living room, using friends who were amateur musicians and singers. In the United States, the music industry arose in tandem with the rise of "black face" minstrelsy. Blackface is a form of theatrical makeup used predominantly by non-black performers to represent a black person. The practice gained popularity during the 19th century and contributed to the spread of negative racial stereotypes of African-American people. In the late part of the century the group of music publishers and songwriters which dominated popular music in the United States became known as Tin Pan Alley. The name originally referred to a specific place: West 28th Street between Fifth and Sixth Avenue in Manhattan, and a plaque (see below) on the sidewalk on 28th Street between Broadway and Sixth commemorates it. The start of Tin Pan Alley is usually dated to about 1885, when several music publishers set up shop in the same district of Manhattan. The end of Tin Pan Alley is less clear-cut. Some date it to the start of the Great Depression in the 1930s when the phonograph and radio supplanted sheet music as the driving force of American popular music, while others consider Tin Pan Alley to have continued into the 1950s when earlier styles of American popular music were upstaged by the rise of rock & roll. Advent of recorded music and radio broadcasting At the dawn of the early 20th century, the development of sound recording began to function as a disruptive technology to the commercial interests which published sheet music. During the sheet music era, if a regular person wanted to hear popular new songs, he or she would buy the sheet music and play it at home on a piano, or learn the song at home while playing the accompaniment part on piano or guitar. Commercially released phonograph records of musical performances, which became available starting in the late 1880s, and later the onset of widespread radio broadcasting, starting in the 1920s,