The inspiration for Altan was sparked when Donegal-born fiddler and vocalist Mairéad Ní Mhaonaigh met Belfast-born flute player Frankie Kennedy. Ní Mhaonaigh had learned the traditional style of fiddling from her father, Francie, who had learned it from his mother, Roise. Influential Irish fiddler Dinny McLaughlin, who frequented her childhood home, added to her knowledge of the instrument. Kennedy, who studied flute as a youngster, was extremely interested in Irish music and made several trips to Ireland during school vacations. Meeting during an informal jam session, Ní Mhaonaigh and Kennedy began to play together at every opportunity. Although they both took jobs as trainee teachers at St. Patrick's College in Dublin, music remained their shared passion.

In 1979, the two musicians made their recording debut as accompanists for Gaelic singer Albert Fry on his self-titled debut album. Two years later, Ní Mhaonaigh and Kennedy graduated from college and were married. Together with bouzouki player Donal O'Hanlan and Mairéad's brother Gearóid Ó Maoinaigh, who played guitar, Ní Mhaonaigh and Kennedy formed a band, Ragaime. Although they recorded for RTE, the group disbanded by the time that Gael-Linn released Ní Mhaonaigh and Kennedy's debut album, Ceol Aduaidh, in December 1983. One track on the album, "An Clar Bog Dell," featured Enya, then known as Eithne Ní Bhraonáin, on Prophet-5 synthesizer.

In 1987, Ní Mhaonaigh and Kennedy recorded their second album as a duo, Altan, named after a lake in northwest Donegal. Produced by Dónal Lunny, the album featured accompaniment by Ciarán Curran on bouzouki, Mark Kelly on guitar, and Mairéad's sister Anna Ní Mhaonaigh, then a member of the all-woman group Macella. Shortly after the completion of the album, the musicians agreed to continuing working together. During the summer of 1988, Altan began work on their first album as a band, which now included Paul O'Shaughnessy on twin fiddle. Produced by Phil Cunningham and released in 1989, the album, Horse with a Heart, featured a more dynamic sound than its predecessors.

As the band's touring schedule expanded, O'Shaughnessy and Kelly were forced by their day jobs to restrict their activity with Altan to recording and performances close to home. During the band's U.S. tours, their places were taken by Daíthí Sproule on guitar and Ciarán Tourish on fiddle. Altan reached top form with their 1990 album Red Crow, which received a NAIRD award as Best Celtic Traditional Album. Their next album, Harvest Storm, released in 1992, received the award as well.

All news was not good for the band, however. In 1991, Kennedy was diagnosed with cancer. Although he was hospitalized the following year, he recovered sufficiently to rejoin the band's tour. On September 19, 1994, he succumbed to his illness and passed away. Altan has continued to bring their music to the international stage. Accordion player Dermot Byrne, who had played on Red Crow and on Altan's 1993 album, Island Angel, joined the group formally in 1994. 1996's Blackwater and 1997's Runaway Sunday were released on the Virgin label before the group jumped to Narada for 2000's Another Sky. Numerous compilations and collections followed, as well as Blue Idol in 2002 and Local Ground in 2005, again for Narada. ~ Craig Harris