To celebrate a culturally diverse Ireland this St Patrick's day, Calypso's new play reminds us our patron saint was once a foreigner, too. Peter Crawley joins the mix.

Calypso Productions have a subtle way of making a point. Ahead of a scheduled visit to rehearsals for Mixing it on the Mountain, Marguerite Bourke, general manager of Dublin's issue-led theatre company, is checking the spelling of my name. "That's C for Cork, R for Russia, A for Argentina . . ." As Wicklow, Lima, England and Yugoslavia trickle down the phone line, the old familiarity of my identity has never seemed so full of intercultural possibilities.

Tomorrow, when a young multicultural cast comprised of professional actors and school students explode the legend of St Patrick in the Samuel Beckett Theatre, a familiar emblem of our national identity will be opened up to the same cross-cultural invigoration.

Developed through Calypso's Tower of Babel programme, which for over a year now has organised drama and musical workshops with young people from ethnic minorities, Maeve Ingoldsby's script concentrates on the patron saint's teenage years - "before the saint thing" - and will follow an ambitious journey through various musical styles.

For Solomon Ijigade, an 18-year-old school student originally from Nigeria, landing the role of the Apostle of Ireland was something of a surprise. "I'd say yes, because first of all I'm not a white guy," admits Ijigade, resplendent in a bright yellow Fubu top and matching baseball cap. "Sorry to use that word, but I'm from Africa. When Bairbre told me [I had the part\], I thought, Oh my God, but I'm a black man!" He apologises again. "I'm sorry to be using 'black' and 'white' still."

Skin-colour was not a hang-up that others shared, and ultimately Ijigade accepted that, "it doesn't really matter, as long as I can fit in." Fitting in, of course, is what Mixing it on the Mountain is all about. As director Bairbre Ní Chaoimh says, "the whole play is about integration". Making an imaginative leap, the play supposes that the Celtic raiders of the fifth century, who abducted slaves from England and Wales, could cast their nets to the further reaches of the Roman Empire. As incomprehension and tensions flare on Slemish Mountain among captured north Africans, eastern Europeans and the indigenous Irish pagans, it is music that provides a common language.

On this point, the cast are effusive. Playful anachronisms score the tale with wailing blues, stirring gospel, a lamenting Irish sean-nós, Macedonian singing, gangsta rap and a love ballad that, according to musical director David Boyd, "Disney would be proud of".

Like the script, the music has been influenced by the experience of the cast. "I asked for tunes," Boyd says of the collaborative composition. "When we need an African song, there's no point in me, a white Irish guy, coming along to teach African musicians what to do." The confluence of musical styles, where traditional Irish rhythms merge seamlessly with their African counterparts, reflects the ease of integration achieved by the cast.

"The music in the show takes it right out of the fifth century and makes it universal," says actor Lisa Lambe, who plays Patrick's love-interest Fionnula. "It's really like having a passport in the room and being able to travel all round the world."

Ijigade agrees. "Music is a common language that can bring everybody together. Without the music, we wouldn't have been able to communicate at all in this show." He should know. His own band, Adun Oyin, performs African Gospel songs in Yoruba and English, which serve devoutly religious concerns. "We are Christians, and we want to preach the Gospel to the world." He must have a remarkable affinity with the proselytising Christian he plays then? "Just trying to be Patrick . . ." he chuckles. And the band's name? "It means the Sudanese are horny." How saintly.

There have been challenges in creating a play around a cast that includes children of refugees and asylum seekers and several unaccompanied minors who are in the care of the health boards. "We didn't want to do anything that was directly related to the experiences of the non-Irish members of the cast," explains Ní Chaoimh, "because their experiences are incredibly personal and private and there are \ reasons they can't speak about them anyway. In some cases, people have very traumatic reasons for being here. So that isn't open season for drama.

"We wanted to find a parallel situation that could be fun, but that would still have resonances - the fact that Patrick was brought here as a child slave, and he went on to become our national icon, is a great irony."

There's also some irony in adopting a figure synonymous with banishment (his legendary aversion to reptiles of the slithering kind) for a lesson in inclusivity. "Yeah," she laughs. "But it's also funny to hear the Nigerians when you're talking about snakes." Among the information and experiences pooled by the cast was the mundane reality of snake deletion in Western Africa. Here's some advice: clutch it by the head, deliver a few fatal stamps, discard.

"You wouldn't just throw them out alive," adds Ní Chaoimh, helpfully.

With such disputed mythology attached to the lead character and, by extension, to the character of the nation, Ní Chaoimh sees an opportunity in St Patrick to play fast and loose with cultural identity, mixing anachronism, historical revisionism, and interculturalism to reflect the changing face of contemporary Ireland. "It's never referred to, the fact that our Patrick is Nigerian. He just happens to be black and he happens to have been brought here as a slave. Where the parallels are, is that there are young people who are in Ireland, and it's not their home. That's the thing I think that people never realise about asylum seekers: it's not that they desperately want to be in Ireland; all of them would love to be living peacefully in their own homes."

Ní Chaoimh insists, however, that there is no heavy-handed message in Mixing it on the Mountain and, rather than setting political goals, the production itself is the achievement. On one level, a community has been formed among the cast that would not otherwise have occurred, relationships have developed free from racial boundaries, experiences have been shared and a mutual understanding has developed. Those new to the theatre now know the difference between upstage and downstage while recognising the concept of the fourth wall. And nearly everybody can deliver a passable version of Happy Birthday in Vietnamese.

On a deeper level, however, this stage provides a model for the kind of integration Ní Chaoimh believes is within Ireland's reach. "This is the first generation in Ireland, I think, that is genuinely multicultural. I know it's possible for people to live together with cultural diversity, and it's so enriching. This group of people represents it.

"Because of our differences, we've created something that's exciting and vibrant. Writers in Ireland haven't caught up yet with what's happened in Ireland. They're still writing plays about the nuclear Irish family or our own political situations. They haven't acknowledged that on the same bus you have all these people living parallel lives."

The finale of Mixing it on the Mountain is a rousing gospel hymn to freedom, performed by a cast that Boyd simply describes as "musically joyful". It is this freedom "to live in your home, to live with your family, to do your own things, to worship your god" that resonates with Ijigade. An international anthem, mellifluous and multi-voiced, placed in the mythological roots of the nation, it achieves the vocal and cultural harmony that Calypso clearly aspires to. "I think we have to reassess what it means to be Irish and to be living in Ireland," concludes Ní Chaoimh.

"Yehudi Menuhin once said, you can only have creativity where there's difference . . . When you have diversity, you certainly don't get what you expect."

Mixing it on the Mountain opens tomorrow and runs until March 22nd at the Samuel Beckett Theatre, Trinity College Dublin. Booking on tel: 01-6082461