It is the scariest thing in the world. You have 2,500 school kids screaming at you. Your blood pressure goes up. You have a smile on your face that you can't control and you don't know why that is."
Putting their instruments aside for a bit, the pupils at St Ambrose High in North Lanarkshire listen intently. One pupil has never been to the Royal Concert Hall in Glasgow before and is shocked to hear how many people it holds. As winners of ScottishPower's Powerful Performance contest, the group will be performing there at the Celtic Connections music festival, in the final education concert.
Today, as part of their prize and in order to help them prepare, popular collaborative performer and teacher Innes Watson, a guitarist, fiddler, singer and composer, has come to the school to give them a masterclass. With little time left, they want to fit in as many rehearsals as possible and some inside knowledge from an experienced performer is welcome.
As well as helping them with the music, Mr Watson - 2011 Instrumentalist of the Year in the MG Alba Scots Trad Music Awards - tells them what it is like performing at the Royal Concert Hall. He advises them to think about the stage plan and how they arrange themselves, and the technical aspects of performing on stage.
"There will be monitors there," he reminds them. "So you will hear yourself through the monitors. It is best to have two guitars loudest for the monitors. It's not favouritism, just less complicated."
There should be no stating the obvious when they talk to the crowd. Announcing "We're going to carry on now" is pointless, he tells them, and sounds silly. Instead, they should interact with the audience by giving a little bit of background on each of the songs. The music is important, but so is the final bow, so the class spend a bit of time perfecting it.
Mr Watson talks to them about aspects of the performance which will most likely never have entered their heads, such as girls perfecting the hair flick when they bow. But he also stresses that they should enjoy the show and let the audience see they are enjoying it, as the audience likes that.
The group of 17 pupils, ranging from S1 to S6, already play together regularly at school concerts and events. While some performed at Celtic Connections last year, this was their first year of entering the competition and they were surprised when they beat schools from all over Scotland.
Heather McDonald, group sponsorships manager at ScottishPower and one of the judges, says: "This is the first time we have run a masterclass for the winners. We wanted to grow the powerful performance and add an extra element to it. There was just something that stood out about the group. They had a collectivity as a group."
Innes Watson was also one of the judges. He says: "Across the board, they were all great and I had expected an easier job. This group was really together, well rehearsed with great arrangements and rhythms."
Fourteen-year-old Lucy Hughes plays the fiddle. "I am very excited, but I'm afraid of slipping up with all the microphones," she says. "Today was really, really good, very helpful. Innes made Lazy March sound even more laid back, and he gave us some good tips such as: if you make a mistake, just improvise."
Ryan Docherty, 15, is an accordion player but unlike Lucy he feels very confident about the performance. "I have played at different venues, but this one still means a lot to me. Today was really helpful and I feel very relaxed. You shouldn't feel uptight about going on stage. Music should be enjoyed."
Mr Watson has no worries about how the group will do on the day. "They are going to be amazing," he predicts. They just needed a wee bit of tightening up, but if they had to perform today they would still be great."
Music teacher Sarah Bonner works with the group and was the one who put them in for the competition. "There was a big hype leading up to it, so more effort than usual," she says. "The Concert Hall is a huge achievement. They have worked really hard, so their playing has improved. It has been great to work with Innes and good for them to work with someone else. We are just teachers, so they don't view us the same as gigging musicians."
Heather McDonald says ScottishPower is "incredibly proud of this competition. We feel it has the opportunity to bring emerging talent through. There is a real focus on education in Celtic Connections."
Over 2,000 groups play the annual Celtic Connections festival, with this year's line-up including such big names as The Proclaimers and Barbara Dickson.
The St Ambrose High group will perform at the final education concert, then take part in the Danny Kyle Open Stage competition for new musical talent.
This is the third year ScottishPower has run its Powerful Performance competition for schools. It is designed to encourage involvement in the arts among pupils and to encourage them to celebrate their Celtic musical heritage by providing them with the chance to perform live at the Celtic Connections.