For about an hour and 40 minutes, give or take, the music plays -- except for the short periods designated as "teach." Eagles coach Chip Kelly says there is a lot of science behind why he has done it since he coached at the University of New Hampshire, but he really did not have time to explain it in a 15-minute press conference.

If it was on Sirius XM, the channel would be described as "from the '80s to today, most of it with a driving beat." It is the most noticeable difference between a Chip Kelly practice and any football practice you have ever seen -- that and the overall tempo of the thing, which is, well, very fast.

For reporters who have seen the last 14 years covering Andy Reid's practices, it was just one of the shocks. The other came at the team's NovCare Complex practice fields, where the rule was always that you couldn't sit down to watch practice, even on the decorative concrete bleachers that are part of the building. Back when, broadcasting legend Merrill Reese sat down on those bleachers and was informed, "They aren't for sitting -- they're achitecture."

And now? The requirement is that after the first couple of periods of practice, reporters are required either to sit on the aforementioned architecture or stand nearby.

Down is up and up is down around here -- and there were more than a couple of reporters who have spent their lives wondering how their kids can do their homework wearing headphones or watching television who now are wondering how football players can learn anything while music is blasting. But here is the thing: to fail to recognize the real revolution in thinking that Kelly represents is to miss out on the story of the season.

Every coach who has ever run an NFL practice -- and I mean ever -- talks about how hard they work and the tempo they try to set and all of that. But, well, trust me -- I've never seen an NFL team work faster than the Eagles worked on Monday morning.

You knew it was going to be a little bit different, early on, when the Eagles ran a drill where all five quarterbacks on the current roster, all in red jerseys, received shotgun snaps simultaneously and threw five different passes to five different receivers with five balls in the air at the same time.

The whole thing runs so quickly, and amid the music and the overall volume of the atmosphere -- that the theory is that the game might actually be easier to handle than the practices.

"The game itself kind of slows down," Kelly said.

Earlier, he said, "I think the game is about quick decisions. It's a game of 60 to 70 to 80 4-second plays...The mission is to be able to play a 4-second play."

Between those plays, the quarterbacks were receiving play calls from offensive coordinator Pat Shurmur, who was barking instructions into a walkie-talke that was connected to their helmets. But everyone else seemed to be getting their information from people waggling in a series of signals from the sideline. Kelly said that not everyone on the field is getting all of their information that way, but you would see everybody -- linemen, backs and receivers -- looking over at the series of hand signals as they lined up for the next play.

Kelly was in the middle of a lot of it, especially early in the practice, even snapping the ball during one drill. He says that will continue. And while all of the team's practices cannot possibly be this hyperkinetic -- for one thing, the roster will shrink considerably from the current 90 players as the regular season approaches -- a tone is being set here. And while Kelly acknowledeged there can be an acclimation process, he said the Eagles' players have been willing learners.

"For us, it's been fantastic -- because they want it," he said, adding later, "They want to learn. They've been great at it...That, for us, has really been refreshing."