In search of happy celtic tunes I would refer you to a non electronic source and that is the Soodlum books. There are at least three or four, 100 Great Scottish Songs and Soodlum's Selection of Irish Ballads Volumes 1, 2 and 3. They also have put out a tape that goes along with the books to give you the tunes if you don't read music but play by ear (like me). There are many happier tunes in these such as Band O'Shearers, Buy Broom Beesoms, The Lea Rig, Maids When Your're Young, Mally Leigh (Archie Fisher did a nice recording of that one), Mary Mack, The Merchant's Son, The Jolly Beggarman, I could go one. As a performer I am always looking for traditional tunes that few and hopefully no one else is performing I do have a couple of other more obscure books which have some happy tunes if you need more.