The music was blaring Tuesday, the same as most days at the Philadelphia Eagles complex, the beat audible for blocks. This is part of first-year Coach Chip Kelly’s system, one reinforced — at least according to the former University of Oregon coach — by research and logic. The Eagles flout NFL convention, and Kelly has altered the weekday schedule, the travel routine and, of course, the music — cranked always to 11.

“A little bit off-kilter” is how Eagles center Jason Kelce described the earliest days inside Kelly’s universe.

And then there’s the offense, a fast-paced, no-huddle attack. Regardless of injuries or criticism or the next Sunday’s defense, Kelly is either stubborn or resolute: His system worked at Oregon, and therefore it must work in the NFL.

“One thing I can say about Chip is he’s not really into switching up too many things,” Eagles wide receiver DeSean Jackson said. “He feels very confident and comfortable with the system.”

Each year, NFL coaches tinker with the league’s elemental makeup with varying degrees of commitment. A change here or there could alter a franchise’s direction and anoint the coach the NFL’s next innovator.

But is it the system or players that wins NFL games? Which is the true complement?

Last year, Washington Redskins Coach Mike Shanahan upended a decades-old system to fit quarterback Robert Griffin III. Though squinted eyes can still see principles Shanahan used with the Denver Broncos, he altered a proven philosophy to match his franchise player’s skills.

“Just because you’ve had success with something in the past doesn’t mean you’re going to have success with it now or in the future,” said Kyle Shanahan, Washington’s offensive coordinator and Mike Shanahan’s son. “And sometimes you’ve got to learn the hard way.”

Kelly, meanwhile, brought his system with him from Eugene, and he already has begun changing the Eagles’ routine and roster to fit a style that won nearly 87 percent of Kelly’s games at Oregon. He has been forced to make minor adjustments this season, but so far he has shown no willingness to abandon the system that brought him here. Mike Shanahan’s changes won the NFC East in 2012 but have the Redskins at 3-6 this season.

Kelly and Shanahan are not the first to take a side on this philosophical spectrum, and the long-term results remain unknown — that roulette wheel is still spinning, and two coaches in Philadelphia and Washington are hoping their choice is best.

Surrendering old habits

The old coach tried it both ways, and neither time did he fail. Barry Switzer won two national championships at Oklahoma in the 1970s with the wishbone offense, stocking and restocking his roster with mobile quarterbacks who could run the option. In the mid-’70s, Switzer instructed a young assistant named Mike Shanahan to learn the option, though Shanahan wouldn’t revisit those early lessons for nearly four decades.

“You don’t forget things like that,” Switzer said this past week.

In 1984, Switzer brought Troy Aikman, a tall but slight prospect, to Norman and installed him as the wishbone’s centerpiece. “We felt like he could fit into our system,” Switzer recalled.

Aikman passed only occasionally, and after suffering a broken ankle in 1985, the young quarterback transferred to UCLA. The Sooners went on to win their third national championship that season with freshman scrambler Jamelle Holieway as Aikman’s replacement.

At UCLA, Aikman added bulk, the Bruins emphasized his passing and he was a consensus all-American in 1988. The Dallas Cowboys drafted him first overall in ’89, and three years later, Aikman led Dallas to the first of two consecutive Super Bowl wins.

When coach Jimmy Johnson stepped down, Cowboys owner Jerry Jones hired Switzer. He had won in college; why couldn’t he do it at the game’s highest level?

Switzer eyed the roster, saw a few familiar faces — but noticed that the quarterback he knew in Norman was different. Sure, the wishbone had worked at Oklahoma, but Switzer said forcing his system would’ve wasted a legendary roster. The NFL, the retired coach said, isn’t as forgiving as college football.

“You have to adjust to what your quarterback’s talents are because you can’t go recruit them,” he said.

Switzer, Aikman and the Cowboys won another Super Bowl after the 1995 season, with Aikman never lining up in the wishbone. Not that the itch ever left Switzer, who approached Jones with an idea.

“You can run the option,” recalled Switzer, who unsuccessfully lobbied Jones to bring in an option quarterback as Aikman’s backup.

Regardless of success, some habits are harder to surrender than others.

Instituting a dramatic change

During the 2012 offseason, Mike and Kyle Shanahan studied footage of the read option, which other NFL teams had run effectively. Mike Shanahan reflected on his days inside the wishbone machine at Oklahoma.

“Everything’s a learning experience,” he said.

Washington had drafted Griffin, an electric runner and a promising college passer, with the No. 2 overall pick. Mike Shanahan had won two Super Bowls in Denver using a zone-blocking scheme that relied on power running and an accurate quarterback. It had worked, but now it was part of the past.

“I don’t think you really have much of a choice,” the Washington coach said. “Whatever players that you have, you have to adapt a system to those players.”

Whether it was adjustment or a survival instinct — the Redskins had gone 11-21 in Shanahan’s first two seasons — Washington instituted a dramatic change, leaving only blocking concepts and terminology and emphasizing a zone-read scheme that frequently ran the option.

Kyle Shanahan said he has tailored offenses to his players in each of his six seasons as a coordinator, dating to his time with the Houston Texans. None were as significant as adapting to Griffin’s skills, and none had higher stakes.

Whether it was the right move or not, Kyle Shanahan said stubbornly sticking to a system — and forcing players to fit into it — is “pretty stupid.”

“Coaches aren’t just going to keep running plays that their players aren’t good at unless they want to get fired and suck at everything they do,” he said. “Eventually you’ve got to adjust.”

Washington has made less noticeable tweaks this season, some to accommodate Griffin’s healing right knee and opposing defenses’ own changes and others to jump-start a sluggish and mistake-prone offense. Its coaches haven’t yet found the right adjustment to replicate last year’s success.

As a result, Kyle Shanahan said, the experimentation at Redskins Park is ongoing.

“You’d better adjust pretty quick,” he said, “and quit beating your head against the wall trying to run something that’s not working.”

Believing a system works

In a quiet Eagles locker room, players insisted their coach isn’t as obstinate as he has been portrayed. Kelce said Kelly has explained his philosophy, and the reasons have so far made sense.

The music is about simulating a game-day atmosphere, the practice schedule is about maintaining momentum and the commitment to the offensive system is about taking defenses by surprise.

“There’s an explanation behind it, and that helps guys buy in,” Kelce said.

A few modifications have proved necessary. Michael Vick, Kelly’s choice as his starting quarterback, has a lingering hamstring injury, forcing Nick Foles, a 6-foot-6 drop-back passer, into the lineup. “Obviously he’s used to running [the offense] with a much more mobile quarterback than Nick,” Kelce said. “I’m not saying Nick is slow or anything.”

Foles — who ran a 5.14-second 40-yard dash at last year’s NFL combine, compared with Vick’s 4.33 at the 2001 combine — is now leading a similar offense, only with fewer designed quarterback runs and an emphasis on deep passes.

“Everything anybody does offensively is always about the players you have,” Kelly said, “and we have good players.”

Mostly, though, the routine and the philosophy are unchanged. The Eagles have won four of their past six games and are tied with Dallas for the division lead, and that’s enough to garner trust in Kelly’s system. After 10 games it’s too early to know whether it’ll change football or where it’ll place Kelly in NFL history. If nothing else, he believes his system works — an accomplished gambler always does — and has convinced players to believe, too, that a big payoff is coming.

“I can admit at first, it was kind of tough,” Jackson said. “We’ve seen how bright it can be for everybody’s future.”