By Paddy O'Flaherty
BBC Northern Ireland
One of the world's oldest styles of religious music is attracting a host of new enthusiasts.
Gregorian chant is usually associated with monks in monasteries, but it's being heard more often now in regular services.
Tutor Donal McCrisken at the Gregorian chant workshop in Belfast
Its growing popularity brought 70 representatives of choirs from Northern Ireland to a chanting workshop in the Dominican Convent in west Belfast.
The college chapel became a study for a day as experts passed on advice on how best to perform the ancient melodies.
Principal tutor Donal McCrisken said Gregorian chant was an excellent medium for vocal training.
"You have to sing it very purely - very accurately," said Mr McCrisken.
"You have to have an absolute ear for unanimity. It has to be exactly together."
Mr McCrisken, who is head of music at St Malachy's College in Belfast, said the music's origins lay in the ancient chants of the Jewish church which were adopted by the early Christian church.
Gregory the Great
Its first major champion was the 6th century Pope Gregory I, known as Gregory the Great.
Nearly 1,400 years later, Gregorian chant is again being encouraged by Gregory's successor, Pope Benedict XVI.
He described the music as "a great tradition."
Mr McCrisken said the music wasn't simply a relic of the past.
Pope Benedict is a fan of Gregorian chant music
"It continues to have a major effect," he said.
"Composers writing liturgical music today - the great composers like John Tavener, Henryk Gorecki and Arvo Part - they are all referring back to that purity of line that you find in Gregorian chant."
The Gregorian workshop was arranged by Schola Gregoriana, a choir formed two years ago by Queen's University students who share a love of the music and its history.
One of the choir founders, Eamonn Manning, welcomed Pope Benedict's encouragement for the music.
"It has always been advocated in the documents of the church," he said.
"We're lucky Pope Benedict has recently highlighted the significance of this music.
"He's known for having a great love of very good music and he sees it as being very important for the liturgy in the modern age."
Eamonn Manning is certain the music will become more popular with modern congregations.
He said: "When it's taught well and promoted properly, with sensitivity to parish clergy and parish choirs, it can really take off and be extremely beautiful."
Donal McCrisken agreed that, to the musical novice, Gregorian chant has a strange appearance, with square notes and only four lines instead of the usual five.
"It is strange-looking music if you haven't grown up with it," he said.
"But it's not as difficult to sing as some people imagine. If you haven't grown up with it, an introduction as we've had in this workshop goes a long way towards removing the mysteries."