Second Lining* for Dummies...and Happy Mardi Gras Y'All
*compliments of Wikipedia: The "first line" of a funeral consisted of the people who were an integral part of the ceremony, such as the members of the club or krewe, or family and friends of the deceased. Usually brightly coloured items such as beads and feathers were offered to the "second line". The "second line" originally referred to people who were attracted to the music. Traditionally such people would follow behind the "first line." (In the final decades of the 20th century it became more common for some such onlookers who joined the procession to mix in or even get ahead of the band and first line, behavior considered a social faux pas by older New Orleanians.)
To follow such processions because one enjoyed the music came to be known as to "second line" or to be "second lining." Uninhibited dancing at processions also came to be called second lining.
"Let's dance, put on your red shoes and dance the blues
Let's dance to the song
They're playin' on the radio
While color lights up your face
Sway through the crowd to an empty space..."--David Bowie