Welcome to second-division club FC Union's 'Weihnachtssingen' – a candle-lit carol concert with 27,500 fans expected to belt out festive songs alongside a choir, a band and a small religious service.

Berlin-based Union, who are currently mid-table in Germany's second tier, have long since sold all the tickets for Tuesday's event, which has become a traditional date at the club's An der Alten Foersterei Stadium in the eastern suburb of Koepenick.

Free candles and song sheets are handed out at the entrance as players and fans sing German carols like 'O Christmas Tree' and 'Silent Night' side-by-side on the pitch or in the stands.

Other German clubs have borrowed the idea with 1860 Munich and Alemannia Aachen now holding their own carol concerts on a smaller scale.

'Christmas feeling with a football atmosphere'

"For me, it's the best of both worlds, you start to have that Christmas feeling with Glühwein (mulled wine) and songs, but with a football atmosphere in a filled stadium at the same time," Union fan Juri Denecke told AFP.

The event has illicit roots when a group of 89 Union fans, carrying Gluehwein and festive biscuits, climbed over the fence to break into the stadium in December 2003 to hold an impromptu carol concert on the pitch with friends and family.

The annual 'secret' gathering spread by word of mouth, grew year on year and is now the biggest event in the club's calendar.

Torsten Eisenbeiser, who helps organise it, was one of the original singers more than a decade ago and is staggered by its development.

"No one at the time thought we would ever reach such dimensions," he admits.

Capacity crowd expected

Due to demand, admission will be ticket-only for the first time this year, with €5 for standing places or €10 for a seat.

The gates had to be closed last December when the 27,500 capacity was reached, leaving hundreds locked out.

"Preparations have been going on for weeks," Union's press officer Christian Arbeit told AFP.

"The biggest problem is getting enough staff, because it's always held the last night before Germans celebrate Christmas and many people are either on holiday or are preparing their own celebrations.

"But we need more employees for that evening than we do for any other night of the year.

"More people came last year than fit in the stadium, so we had to limit numbers and the fans voted to charge five euros, with the money going to the club's youth section.

"All members got a free ticket to give as many people as possible the chance to come.

"And it also gives long time Union fans, who built this place and kept the club alive, a little advantage."

Arbeit is not only involved in organising the event, he will be playing in it.

"We try and keep the programme as familiar as possible," he explained.

"There is always a choir from the same school in Köpenick and a parish priest from the town, while my parents and I will be on the trombone, clarinet and trumpet — like a small family celebration.

"So we can all feel at home — even if there are now so many people."

The pitch will be well protected after the 2012 event cost the club a quarter of a million euros because a new playing surface had to be laid after heavy rain and thousands of trampling feet ruined the grass.

While neighbours Hertha Berlin ply their trade in the Bundesliga, Union's supporters have carved out a reputation for social initiatives.

When the club lacked the funds to renovate the stadium six years ago, around 2,500 fans gifted 140,000 work hours between May 2008 and June 2009 to make sure the modernisation was completed.

And in 2004, with the club facing bankruptcy, supporters organised the campaign "Bleed for Union" where fans gave blood and forwarded the nominal fee donors receive in Germany to the club.