American Popular Song: Message board and directories of singers, songwriters, movies, and shows.
American Popular Song: From paper presented by Howard S. Becker at a 1994 conference discussing the structure of the standard popular song along with its history, songwriters, musicians, and singers. Bibliography.
AMG: Vocal Music: Overview of the genre, essay, key artists and albums, and recent releases.
Craig's BigBands and BigNames: Historic reviews and photos from performers of the 1940s, 50s, and 60s. Includes old time radio broadcast, quiz, and message board.
Ian Whitcomb's Literary Corner: Includes articles on Rudy Vallee, Duke Ellington, Irving Berlin, and the first crooners.
JD Hay's Crooners: Library of songs in WAV format, including those by several pop artists and a 1950s collection.
Jukebox: American Popular Music in the 1930s: Includes 40 audio files, with background and commentary.
Parlor Songs: Collection of popular and classical sheet music from the 1800's to the 1940's, cover art, audio samples, composer biographies, and articles on the history, styles, and themes.
Wikipedia: Melodic Music: Defines "melodic" genre as the vocal-oriented popular American music style that came after big band music but before rock and roll, as exemplified by singers like Perry Como and Margaret Whiting.