The singing is the flanges momentarily hitting the rail - if the flanges actually rode continuously against the rail it would be more of one long continuous screech.
And yet this incredibly brilliant guy sounds like a brawler from the heart of Brooklyn. Had he been lecturing, I never would have had to drop the quantum physics class I took in college. There's a series of talks he gave at Cornell on various aspects of partical physics that are on YouTube and quite understandable. Of course, no one compares to Fenyman when giving a lecture. At any speed, until inertia overcame friction, it faithfully followed the curve in the track. Next he took a piece made of two cones glued together, fat part in the middle, tapers outward. Of course, it hit the curve and apart from a slight deflection, ran right off the table. He laid out a J shaped section of track and rolled a cylinder down it, starting on the straight vertical leg of the J. Richard Hammond (you might know him from the original British Top Gear show) did another show on engineering marvels, and in one episode demonstrated very clearly that it's the wheel taper adn not the flange that keeps the train on the track.
