The dancers in this video are having a good time, but I think they're just waltzing. There's a lot of foot-stomping in a Ländler.
Elmer Scheid led a polka band for fifty years, based in New Ulm, MN. He recorded 15 albums and influenced a lot of concertina players. YouTube has tons of these KEYC-TV Bandwagon polka videos. They're not all exactly electrifying in terms of energy, but the Elmer Scheid band sounds great, even transcendent at times. I wonder, how did they learn their arrangements? Did Elmer hum a part to each musician, Basie-style, and have them play it over and over until it was second nature? Or were parts written out and memorized individually?
My favorite song at the moment is Scheid's Two Canaries polka. There's no video of him doing it, but there is this concertina version that I really love as well, despite a wrong note or two —
Finally: Scheid's "My Millie's Waltz", video posted by the above concertinist —