The other day my buddy Tom asked me what a Second Line is and I froze in horror because if any of my out-of-state friends ask me this question it means that I have not done my job as a New Orleanian. And since I am not just a New Orleans woman but also a nerd I will first give you the wikipedia definition:
The "main line" or "first line" is the main section of the parade, or the members of the actual club with the parading permit as well as the brass band. Those who follow the band just to enjoy the music are called the "second line." The second line's style of traditional dance, in which participants walk and sometimes twirl a parasol or handkerchief in the air, is called "second lining." It has been called "the quintessential New Orleans art form — a jazz funeral without a body." Another significant difference from so called "jazz funerals" is second line parades usually lack the slow hymns and dirges played at funerals (although this is not a hard rule; some organizations may have the band play something solemn towards the start of the parade in memory of members deceased since their last parade).
NOTE! You absolutely do not need a parading permit to second line. In fact, if you can get your hands on a brass band right now, you can dance behind them in your living room with a parasol and it's completely legal. And even if it is illegal where you live, a New Orleanian would never arrest you. We would just grab a handkerchief, wave it in the air, follow you around your house, holler things, and drink all of your alcohol. Topless.
When my family Second Lines at weddings we play this song But it doesn't have to be that song. The last wedding I went to for my cousin's daughter, since there were no handkerchief or umbrellas, we grabbed napkins and paraded behind the bride and groom and none of us even stopped to get a permit first. I have just looked online for footage of something like this, but all I can find are clips of brides and grooms Second Lining through the French Quarter and you can only really hear police sirens.
A better example is You Better Second Line which is a clip from a Jazz Funeral for singer Juanita Brooks. The beginning is slow but theatrical, I think, with the dramatic flourishes of the women in the beginning. After they walk from the grave (at precisely minute 4:40) things really pep up. Feel free to dance around your computer when it plays, and if you do, not only will you not be fined for not having a permit, but you will technically be Second Lining at a Jazz Funeral. In fact, I dare you to hear that whistle blast at minute 4:40 and NOT (at the very least) dance in your seat.
So those are the basics. If anyone has further questions about Second Line feel free to post questions in the commentary. New Orleanians are standing by. Well, they're not really STANDING. They're dancing, and drinking wine from plastic cups at 6:00 in the morning. Hey! You over there! Focus! These people have questions! And for heaven's sake, put your shirt back on!