World Fleadh:Ireland's biggest session trail kicked off as part of the second World Fleadh in Portlaoise, Co Laois, yesterday.

As well as a céilí, a performance from Jack L and the first of a series of masterclasses with top musicians including Jim Higgins on the bodhrán and Ronan Browne on the uilleann pipes, sessions were held in 21 of the town's pubs.

The World Fleadh Irish and Celtic Music Festival runs until Sunday. Over the course of the week, organisers estimate that more than 640 musicians will perform in the participating pubs.

"The World Fleadh is growing and growing," said festival director Eric Cunningham. "Last year there were 10 pubs involved in the session trail. This year there is double that."

Among the 600 acts confirmed are a number of internationally-acclaimed performers including The Proclaimers, Katie Melua, Deacon Blue, Hothouse Flowers, Carlos Nuñez and Salsa Celtica.

"We always set out to have a line-up of top traditional musicians and we have a mix of Celtic traditions and overseas influences. We want to open people up to different types of music," said Cunningham.

"They might come to see Deacon Blue and discover a band they'd never heard of in the meantime."

The World Fleadh is hoping to follow on from the success of the inaugural festival in Ballybunion, Co Kerry, last year, which attracted 50,000 visitors.

This year the organisers are expecting 80,000 punters over the course of the festival, which will generate at least €20 million for the local economy.

The World Fleadh is based on similar Celtic-themed festivals across Europe and the US, such as those at Lorient in France and Milwaukee in the US.

According to the organisers, they wanted to bring Irish singers, musicians and dancers together for a week-long national event, while also introducing the Irish audience to new types of music.

"I've played all sorts of great festivals around Europe - in Belgium, Denmark and Holland - and in the US, but there was never anything of that scale here," said Frankie Gavin, who has recorded 16 albums with the group Dé Dannan and will be performing at the World Fleadh with his new group, Hibernian Rhapsody, ahead of their performance at Slane Castle later this month.

"Loads of musicians have been going abroad to get that kind of audience. It's great that we finally have it here too," said Gavin.

Another musician who will be performing is leading harpist Triona Marshall, who is originally from Portlaoise. She has played with the RTÉ Concert Orchestra and on this occasion will be collaborating with step-dancers Jon and Nathan Pilatzke from Canada and Cara Butler.

"Portlaoise has really come a long way and it will be great to share the community feeling with everyone who comes for the fleadh," said Marshall.

"The line-up is wonderful and everyone in the town has been really looking forward to it."

To facilitate the festival, a 1,500-seat dome and a big top with a capacity of 5,000 have been erected in the town. As a result of the bad weather, all the major concerts that were due to be held outdoors will now take place inside the specially constructed big top.

As well as music performances, there will also be theatre, céilithe, workshops, demonstrations, masterclasses and a craft fair.

Tonight, the Five Counties Céilí Band will perform at the céilí from 10pm, while the Wolfe Tones will play at the festival club at midnight.

John Dunne, a traditional music fan who runs the Éistmusic club in the town, said the festival would undoubtedly boost business in Portlaoise.

"There'll definitely be a buzz about the town. People like myself have had to travel to see more unusual bands and now they're coming here," he said.

"The diversity of the line-up is impressive and there should be something for everyone."