Karaoke, turns out, was one of Allen's favorite pastimes after hockey.
"He was just a fun guy to be around," Kadlec said.
After a long and successful run, Allen stopped singing yesterday. The Flyers' first-ever coach and Stanley Cup-winning general manager passed away at the age of 90. He died peacefully in an assisted-living facility in Delaware County after a lengthy battle with dementia.
Allen, one of six general managers to preside over the Flyers in 46 seasons, was hired as the team's first head coach in 1966 by then-GM Bud Poile. He remained as a Flyers executive vice president until his passing, joining chairman Ed Snider as the only other team employee still serving continuously since Day 1.
Nicknamed Keith "The Thief" by Daily News beat writer Bill Fleischman in the 1970s for his trades that turned the Flyers into champions, he was inducted into the Hockey Hall of Fame as a "Builder" on Sept. 21, 1992.
"Keith was the first coach in the history of the Philadelphia Flyers and a man for whom I have a tremendous amount of respect," Snider said in a statement. "In my mind, he was and always will be one of the greatest general managers in the history of hockey. I never knew of a bad deal he made. This team never would have reached the level of success we have had over the past 48 years if it were not for Keith.
"Over the years, he became one of my closest confidants and one of my best friends. I will never forget all of the many memories we shared together."
News of Allen's passing stirred sympathies and well-wishes from around the hockey world. NHL senior vice president Jim Gregory had not heard of Allen's death when contacted by the Daily News at his home last evening.
Gregory, 78, first met Allen in 1966 in the Western Hockey League, where Allen was coach, general manager, bookkeeper and publicist for the Seattle Totems before joining the Flyers.
Gregory would go on to become Allen's GM counterpart with the Toronto Maple Leafs from 1969-79 and the two became close friends.
"That is just terrible, heartbreaking news," Gregory said. "If I started talking now and ended tomorrow, I'm not sure I could tell you what an unbelievable man Keith Allen was. He was very intelligent, a knowledgeable hockey guy, but a kind man who was extremely well-liked. Even when we were trying to beat each other, you couldn't help but like him."
Gregory, chairman of the Hockey Hall of Fame selection committee, said he would have to go back and check his records, but he believed Allen was a unanimous choice for the Hall.
"Keith Allen always found a way to bring exceptional talent to Broad Street and weave it into the fabric of a team that would succeed and endure at the highest level, because in Philadelphia, for his Flyers and their fans, no other level was acceptable," NHL commissioner Gary Bettman said in a statement. "The National Hockey League sends heartfelt condolences to Keith's family, to his friends and the Flyers organization, which has lost one of its patriarchs."
Allen played in 28 NHL games as a defenseman for the Detroit Red Wings. He was a member of the Wings' 1953-54 Stanley Cup championship team.
Allen led the Flyers to a West Division title and a playoff appearance in each of his only two seasons (51-67-32) behind the bench. He was promoted to general manager on Dec. 22, 1969 and served in that role until May 27, 1983.
At the helm, Allen transformed the Flyers into the "Broad Street Bullies." He reacquired Bernie Parent from Toronto in 1971, traded for Barry Ashbee, Bill Flett, Rick MacLeish, Ross Lonsberry, Andre Dupont and Reggie Leach.
Allen was responsible for drafting Barber, Propp, Bill Clement, Paul Holmgren, Ken Linseman, Ron Hextall and Pelle Lindbergh. He signed Tim Kerr and Dave Poulin as free agents and traded for an injured Mark Howe, who became a Hall of Fame defenseman.
Bobby Clarke, a shaggy-haired kid with diabetes from Flin Flon, Manitoba, signed his first-ever NHL contract for $14,000 in the front seat of Allen's car in 1969.
"He, more than anybody, was responsible for winning the Stanley Cup," Clarke said yesterday. "Keith was one of those men you rarely come across who was fatherly, grandfatherly to all of us players and our families, yet was tough enough and strong enough to do what was necessary so that we had the right pieces in place to win the Stanley Cup.
"Any player who ever played for the Flyers liked him. He was maybe the only man in hockey who everybody liked. He was a wonderful, wonderful man and one of the best general managers of all time."
Despite presiding over a polarizing Bullies team, Gregory said no one in the NHL dared question Allen's hockey acumen or keen eye for talent.
"Violence in hockey. Violence in hockey," a fuming Allen was once quoted as saying. "I'm going to kill the next person who asks me about violence in hockey."
In addition to Stanley Cups in 1974 and '75, Allen's teams reached the Stanley Cup finals two other times during his 14 seasons as GM. Only Clarke (713-437-199) has a better winning percentage among Flyers GMs than Allen (563-322-194).
Allen was known as a family man who always made sure his players were properly provided for, even if it wasn't in Philadelphia. In 1978, he orchestrated a trade of Joe Watson to Colorado, at Watson's request, since the Flyers no longer had a full-time role for him. Watson soon returned to the Flyers after his playing career - and never left.
Watson and many other Flyers players continued to visit Allen in recent years despite his failing health. With two Stanley Cup rings on their fingers, an incredible bond with teammates and a new city to call home, they felt they owed everything to Allen for the opportunity to be a Flyer. Turns out, Allen helped make what it means to be a Flyer.
"He was an absolute gentleman," Kadlec said. "There was no respect for anyone in the game higher than him; we saw that in our travels."
Courtney Keith Allen was born on Aug. 21, 1923 in Saskatoon, Saskatchewan. He is survived by his wife of 65 years, Joyce; sons Brad and Blake; daughter Traci and grandchildren Chelsea, Shay, Jillian and Chase.
Services were pending.
On Twitter: @DNFlyers