When Dennis Cross ’65 takes the stage in Woolsey Hall tonight to sing with fellow Whiffenpoof alumni for the Whiffs’ centennial, it will be for the second time this year.

Though this weekend’s festivities are billed as “The Whiffenpoof Centennial Reunion,” the Whiffs have been celebrating their centennial since January, when the Whiffenpoofs of 2009 gave a large concert in Woolsey Hall featuring comedian John Hodgman ’94 and former Whiffenpoof Jonathan Coulton ’93 as well as several groups of alumni.

The Whiffs decided to host two large centennial bashes, spread nine months apart, to allow for almost a full year of Whiffenpoof celebrations, said Cross, who is also the president of the Whiffenpoofs Alumni Association. Last year’s Whiffenpoofs were largely responsible for organizing the January concert, which — despite featuring several groups of older singers, including Cross — mainly showcased the talents of what was then the youngest generation of the country’s oldest a cappella group.

“The Whiffs of 2009 wanted to have a celebration that … was really their concert,” Cross said. “The coming together of all the ages — that’s what we’re doing here today.”

Because January is the actual month in which the a cappella group was founded over 100 years ago, this past January was the perfect time to kick off the centennial, said Barry McMurtrey ’88, who began planning the centennial celebrations about a year and a half ago. But most Whiffenpoof reunions, which occur every five years, are held in October, making this month a logical choice for the biggest Whiffenpoof reunion in recent memory, he said.

Though they are a Yale institution, the Whiffenpoofs rarely sing on campus, and the concert in January was meant to give the local community a chance to hear the group, Cross said. Heavily advertised, it packed the 2,700-seat auditorium to capacity. But this weekend is for all Whiffs, old and young.

The next few days cap 10 months of Whiffenpoof activity, including gatherings of alumni in San Francisco, New York, Palm Beach, Nantucket and Cape Cod, McMurtrey said. Throughout the year, groups of Whiffenpoofs of all ages have met to rehearse for this weekend’s concert and begin welcoming the newest Whiffenpoofs.

“The idea was that they didn’t want to just have one day where everyone sort of like jumped onto Yale and then peaced out,” current Whiffenpoof Scott Hillier ’10 said. “It gives us a large amount of time for us to connect with the alums and allows all the alums to participate.”

Hillier added he and the other current Whiffenpoofs, who were tapped from non-senior Yale a cappella groups in April, attended many of the smaller reunions for free.

Besides wanting to spread out the festivities, McMurtrey added, the organizers wished to accommodate elderly alumni who might not have wanted to travel to New Haven in midwinter.

But practical considerations aside, the organizers of the Whiffenpoofs’ centennial simply felt the Whiffs’ 100th year merited an extended celebration.

“That was really for Yalies to come back and for students — to really get the campus interested in hearing a great musical tradition at Yale again,” McMurtrey said. “This weekend is primarily for ourselves to reminisce and throw a birthday party.”