This dance existed just as long as the first two, but seems to have gained most of its popularity during the 2-Tone era (1980's, primarily in the U.K. If this isn't familiar, I suggest you read the alt.music.ska FAQ). It has become a powerful standard for discrimination in "the scene"; people who have been going to shows for a year or two often complain that newer arrivals aren't familiar with this dance. Ironically, considering its popularity, it is the most complex to describe. This quality prompts the very common response, "you have to just go to shows and watch everybody else"; that's actually not a bad idea, but not very helpful either. Here's a decent step-by-step how-to:
1. Listen to the music carefully. When you can sort out the beats (the constant 1-2-3-4 of the song, easier for some people to catch than for others), you should begin by alternately putting each foot forward and taking it back, forward on the odds and back on the evens. This is similar to a two-step, in ballroom terms.
2. Next we add the arms. The elbows stay bent, and the hands are balled into fists; the right hand comes forward when the left foot is out, and the left hand comes forward when the right foot is out. When a hand isn't forward, it ought to come back about as far as the hip. This coordination can be tricky- it's the step my mother and grandmother have been having the most difficulty with.
3. To make it look a little smoother, it helps to bob your head along with this movement. If your head goes down on all the ordinary beats (1-2-3-4), it comes up on all the upbeats (the little "ands" in between).
VARIATIONS ON A THEME
That's it for the basics. Elaborating on this takes a little practice. One variation is "bouncing" your fists on the beats. More popular among the skinheads is a variant where the knuckles are pressed together the entire time, and the elbows swing very wide. Sometimes, you can mix in 4 beats of double-time, dancing at twice the speed -- it looks like 4 quick rabbit punches -- this move is demonstrated somewhere in the video for "One Step Beyond". Another move for interludes of double-time is a spurt of running in place with your knees coming way up high, a la "the Blues Brothers".
While people usually skank side-by-side in rows facing the stage, I've encountered variations to adapt this dance for two people. One is to simply do the dance facing someone. This looks best if you're NOT a mirror image (i.e., you should each put your right foot in at the same time. Hokey Pokey, anyone?). Another is to do a pinwheel, each person following the other in a circle. Both of these require a bit more coordination than dancing alone, in order to stay in synch. Also, these variations take up more room; you'll only get enough space to do this at a show when the floor is not crowded, or if other patrons back off in fear of your flailing limbs.
The amount of variation only increases in today's world where ska mingles with Swing, Latin, and Punk influences. I find that one thing holds true for these hybrid genres: Say you're listening to a band whose sound you could characterize as "Latin ska". Some songs use rhythms to which you could either do "ska dances" or Latin dances, interchangeably.
Others alternate between one type of rhythm and the other in separate sections of the song. The latter is often the recourse of unskilled bands which don't understand the technique required to blend gently from one rhythm to the other, although sometimes good bands will pull this alternating maneuver off well.
WHAT DO YOU DO WITH ALL THIS?
This is, of course, your decision entirely. You may decide that the only benefit you derive from this piece is to be better informed on the opinions and practices of the people you always saw around you at shows and never understood. On the other hand, if you've always stood there tapping your foot, really wanting to bust a move, but been very concerned about how to get started, you're the person I wrote this article for. If it gives you any confidence and guidance, then I've accomplished what I wanted to do.
I don't expect anybody to take their first stab at dancing at a show. It's a lot less frightening to "test-drive" some moves somewhere you feel safer (i.e., at home in front of your stereo). Once you feel comfortable enough to dance in public, it can open up an entire new realm of social possibilities. Never mind how nice it is to have the confidence to ask someone else to dance; the feeling you get when someone else asks YOU is phenomenal.