 The jukebox industry continued to grow through the Great Depression and advertised heavily in Billboard . This led to even more editorial focus on music . The proliferation of the phonograph and radio also contributed to its growing music emphasis . Billboard introduced a " Record Buying Guide " in January 1939 . In 1940 , it introduced " Chart Line " , which tracks the best @-@ selling records . This was followed by a chart for jukebox records in 1944 called Music <unk> charts . By the 1940s , Billboard was more of a music industry specialist publication . The number of charts it published grew after World War II , due to a growing variety of music interests and genres . It had eight charts by 1987 , covering different genres and formats , and 28 charts by 1994 . 
