Errigal is covered with snow again this year. It seems the Frankie Kennedy Winter School in Dunlewey, Co Donegal, has a willing stage-manager in nature. A willing, if an impractical one. Again this year, cars are snaking down the b≤ithr∅n to the Lakeside centre to the traditional music classes and very special concerts beneath Errigal.

On Saturday night, the moon sat like a hard-boiled egg in the night sky, turning Errigal and the lakes silver as we crept down to the centre.

It was a typical Frankie Kennedy winter school concert in that it was unique. Mβire Brennan, the Donegal diva at the centre of Clannad, had almost never played a concert in her solo identity on her home turf. In truth, she will always have to slug it out with her Clannad persona when she plays with her new band.

That's never more true than here, where traditional music groupies are far more likely to yearn for the voice of early Clannad - which is very hard to beat - than the Enya-like soundscapes of the more recent past.

Playing support completely unannounced, to the point that the winter school organisers themselves were gobsmacked when they saw her on stage, was another diva dealing with the powerful ghost of past triumphs, Hazel O'Connor.

She was fab. An edgy, almost frightened presence, she had only drum and harp to support her sharp, emotional voice. The voice seemed made to follow the moonlit walk, as clear and unforgiving as the light, as craggy as the poisoned glen, as true as the shape of the mountain. Sounds stupid, maybe, but hear O'Connor sing her signature classic, I wonder if you'll stay now - "You drink your coffee, I'll drink my tea" - and it's likely you'll be making stupid comments too.

The effect of this tiny venue under the mountain at the lost time of the year is to make musicians reassess and change direction. O'Connor is obviously going back to the folk origins of her balladry to remake her- self as a singer, after the terrible disappointments of stardom. It is certainly working.

Her version of Spancil Hill, with harp and drum, reawoke the ragged tragedy of the song. But perhaps the highlight was For Rebecca, a song about a young friend who died of cancer. O'Connor dedicated it to "all people who've moved on" and you couldn't get a better requiem for Frankie Kennedy himself, Altan's flautist, who died of cancer at 38 in 1994. Her lyrics and her voice achieved a sense of the emptiness death leaves among those who remain.

Mβire Brennan was responsible for bringing this bonus to the stage, but she herself could not have a more different presence. Peaceful and motherly, when she raised her arms of her cloak-like dress she looked like a priestess. Peace is a grand thing to have, but it's useless on a stage. Brennan may have found a new spiritual wholeness, but it's not showbiz.

She and her young band, playing keyboard, flute, whistles, guitar, drums and adding vocals, presented a smorgasbord of solo and Clannad work, including strong numbers such as Coinnleach Ghlas an Fhomhair, In a lifetime, Harry's Game and The Big Rock, but the formula remained fairly constant: Brennan's haunting soprano floating over a lush wash of harmony and instrumentals.

There seems little doubt but that it has some roots in the traditional singing style of her area of Donegal, the singing session at the local hotel that afternoon had featured voices like that of Nora Diver, which were ghostly and lingering in the same way hers is. The other element of influence is surely the church choir with which her mother has been involved.

Put the two together, and you have something which sounds sacred but pre-Christian, perfect as soundtracks for movies such as The Last of the Mohicans (in fairness to the band, they thought the suggestion that they should sing in Irish was ridiculous and Brennan learned some of Mohican and Cherokee for the song).

Her little sister Enya has arguably perfected the cocktail, and is currently enjoying her payment for the soundtrack to Lord of the Rings.

The highlight of the night was brought to us by different sisters entirely. Dee Brennan was invited on stage and winkled another sister, Brid∅n, out of the crowd. Suddenly the dead hand of choral arrangement was no longer upon the gathering. It was a vintage Frankie Kennedy Winter School moment, as the three Brennan women jammed on two magnificent early Clannad numbers, Nil sΘ in a Lβ and SΘ mo mhargadh dΘanta, with their spiralling eastern arrangements and native punch.

It's the kind of thing which makes people brave wind and weather to get here and which will pack the little venue this week for Altan's two traditional homecoming concerts.

Altan's two concerts are on tomorrow and Wednesday. For information phone 087-9309656