The singers of the Zurich Boys' Choir have been delighting audiences for almost 50 years with their traditional Yuletide concerts.
The choir is all the more remarkable for the fact that there is no great tradition of boys' voices in Switzerland. But the enthusiasm of the singers – who all sing in the choir in their spare time – is palpable.
Accompanied by the Hungarian Remenyi Orchestra, the boys will be performing two concerts at the Fraumünster Church - famous for its Marc Chagall windows - on the last weekend before Christmas.
For young members Daniel Molino and Matthias Flückinger, it is a big occasion.
"I'm singing solo for the first time so I'm excited and a little nervous. There's a lot of pressure," Daniel told swissinfo after a pre-concert rehearsal.
"I'm also a little bit nervous because I'm also a soloist for the first time, but I've already taken part in the Christmas concert several times," added Matthias.
Just watching – and listening – to the boys reveals how much they enjoy singing together.
It can sometimes be hard work, says another young singer, Konstantin Helg, but all in all, it's great fun.
The choir, which accepts youngsters from the age of eight, was founded in 1960 by its conductor Alphons von Aarburg. This was also the year of the first Christmas concert.
"There are some concerts where we only sing classical music and there are also concerts which are more for the wider public, with Christmas songs and perhaps a big star," he told swissinfo.
"We always try to do something new but if you have been doing it for almost 50 years it's not always possible."
This year there will be performances of works by Vivaldi and Josef Hayden, as well as some popular Christmas songs.
The Zurich Boys' Choir is one of only a few in Switzerland. Unlike other countries, the choristers train in their spare time and participation is entirely voluntary.
"England has the best boys' choirs in the world, next to, perhaps, the Vienna Boys' Choir and another famous choir in Spain," von Aarburg explained.
"We don't have this tradition but we are working on it. We don't have boarding schools where boys' voices are gradually trained."
The Vienna Boys' Choir in neighbouring Austria, for example, has a grammar school which talented boys can join from age ten. The choir tours and gives up to 300 performances a year.
In England, many of the most famous ensembles, such those at Westminster or Canterbury, are associated with the church.
The Zurich choir is made up of around 120 youngsters. "We have many Swiss but also Germans, Hungarians, boys from China and Japan and other countries. We have many religions but we are a non-confessional choir," said von Aarburg.
Boys can first join an afternoon singing school around the age of six. They then graduate to the choir, with a few making it to soloists. Those wishing to continue after their voices have broken can perform with the men's choruses associated with the group.
The Zurich choristers' amateur status has been no barrier to success. They have recorded several CDs, including one of Christmas songs, and most recently toured in Russia.
They have also appeared with big names, such as with the late conductor Herbert von Karajan, and several singers have starred in Zurich Opera House productions.
The boys say they are looking forward to tackling Haydn and Vivaldi in the Christmas concert. German carols will also be sung, as will a few from further afield.
"For us Swiss the new discoveries are the English Christmas carols which are particularly lovely," von Aarburg said.
And for many Zurich residents as well as for proud Mums and Dads, Christmas without a concert by the Boys' Choir - wearing their blue and white outfits and singing their hearts out - would, quite simply, not be Christmas.
swissinfo, Isobel Leybold-Johnson in Zurich
A family affair
The choir is run by Alphons von Aarburg, who was born in 1938. The former head music teacher at a teachers' training college is also the choir conductor. Both his son and wife are involved in the choir.
The choristers have recorded a number of works, including, most recently Missa Sancti Francisci Seraphici by Johann Michael Haydn.
The choir receives some funding from the Zurich authorities and has been named in the media as one of the city's cultural figureheads. Last year's Christmas concerts were a sell-out.
This year's concerts take place on December 20 and 21.
The choir of the Fraumünster Church includes 5 large stained glass windows designed by artist Marc Chagall.
The stunning windows, each depicting a Christian story, were commissioned in 1967, when the artist was 80.
Also worthy of note are the windows in the north transept by Augusto Giacometti, cousin of Swiss artist Alberto (1945).