Parlor songs from how far back? Stephen Foster was a fellow who was The, or one-of-The First in America to decided that he would make a living composing songs for the purpose of folks all across the country gathering around the Piano (or other various instruments) in the Parlour to sing the latest songs--preferrably his. "Etheopian Minstrel Songs" were popular in his time, & he wrote several such as "The Old Folks at Home" -- "Way Down Upon the Swannee River, Far, far away . . ." There are many websites devoted to his Music. I believe there was a PBS TV special about him & his Music.
    Of course, Tin Pan Alley was later on, but it was about selling sheet Music of songs & instrumental pieces to the general population as a form of entertainment--songs/pieces which would hopefully become popular for muking music in the Parlour--thus "pop" Music.
    Imagine a song so popular that it sweeps across the USA from coast to coast withOUT planes, Movies, radio, TV or even Victrolas. It happened with some of Stephen Foster's songs. Now THAT'S a Parlour Song!