Clancy Brothers - everything. It all started with them.

In more detail:

Clancy Brothers>Ryan's Fancy>Planxty>Clannad>Dolores Keane>Sean Keane
Tannahill Weavers>Battlefield Band>Alistair Brown>Old Blind Dogs>Brian MacNeill>Janet Russell

Johnny Cash>Ralph Stanley>Nitty Gritty Dirt Band>Doc Watson>Gillian Welch>Joe Newberry

Steeleye Span>Fairport Convention>Martin Carthy>Waterson,Carthy>Eliza Carthy>Crucible

Pete Seeger>Geoff Warner

Garolou>La Bottine Souriante>Entourloupe>Serre L'Ecoute