'Big Sing' hope at Nos Galan races in Mountain Ash
Organisers of the Nos Galan races in Mountain Ash are hoping thousands of people will join together to sing Calon Lan at the event.
It has come to light this year that the Welsh hymn was composed in the Cynon Valley town and it has been adopted as the anthem of the New Year's Eve event.
The crowd will be led by the children of Cae Garw primary school who have researched the history of the song.
Each year a famous mystery runner joins thousands in the 5km road races.
Rhondda Cynon Taf council said there were two mystery runners this year, "who play the same sport and both proudly represent their country at the highest level".
Their identities will be revealed on Saturday night.
Local councillor Andrew Morgan, of the Nos Galan committee, said: "We are delighted to once again have two great sports people representing the spirit of Guto Nyth Bran."
Organisers hope that in addition to that tradition, crowds who gather in the town for the event will now also take part in an annual "Big Sing" of Calon Lan.
The Cae Garw pupils discovered that the hymn was written by Daniel James when he was living in the town and first performed at Bethania Chapel in Mountain Ash in 1910.
The children have been viewing census results, using the local library and speaking to residents to further their research.
They have held an exhibition in the town library and given presentations about their work to community groups.
Deputy head teacher Huw Griffiths said it had been an important project for the children to find out about the history of their community.
"More and more people have come out of the woodwork to help us and the the community has really taken it to its heart," he said.
"We've had people contacting the school saying they are a relative of Daniel James, and they're living in the Mountain Ash area.
"We've had the parents and the local library involved. We've been to the day centre and Troedyrhiw homes to show our research. It's been very exciting"
The children have performed Calon Lan to the founder of the Nos Galan races, the former commonwealth GB athletics team manager Bernard Baldwyn.
He started the races in 1958 to commemorate the life of the 18th Century runner Guto Nyth Bran.
It is a festival night in the town with a funfair and fireworks. Hundreds of runners participate in the children's races, elite adult race and fun run - including one celebrity mystery runner.
In the past they have included figures such as Olympic gold medal-winning athlete Linford Christie and footballer John Hartson.
Organisers have said the mystery runner at this year's event will be a high profile figure.
About 1,000 runners participate in the races with up to 10,000 spectators.
In nearby Llanwonno a wall of photographs celebrating previous mystery runners has recently been unveiled.
Mr Morgan, who is on the organising committee for the races, said it is an important night for the town.
"Mountain Ash has been put on the map through Nos Galan. The town centre is absolutely crammed to capacity," he said.
"We get runners from all over the place. There's been one from Dallas, in America, we've had runners from South Africa. We've had a number of entrants from across Europe.
"It does draw in thousands of people. It's an extremely popular event which helps the economy of the town."
The words of Calon Lan will be printed in the event programme and projected onto the walls of buildings in Mountain Ash.
A group of children from Cae Garw Primary school will lead the singing.
The organisers hope that Calon Lan will become inextricably linked to Nos Galan and the Big Sing will become an annual event on New Year's Eve.