As a starter, 3 CDs with audio clips are HERE. The Fiddler's Companion says:

DARK LOUGH NA GAR (Loc Dorca Na Gar). AKA - "Dark Loch na gCaor," "Dark Lochnagar." Irish, Air (6/8 time). D Major. Standard. AABB. Gearoid O' hAllmhurain believe this tune may have been learned in County Clare from Scottish sappers in the 1830's who were sent to the region as part of the British survey of the country. Whatever its origins, it became the melody of a popular 19th century song circulated on ballad sheets (the ballad gives reference to the Scottish battle of Culloden, in 1746). Recorded by Clare piper Robbie Hannon. Piper Jimmy O'Brien-Moran says it was a favorite of Willie Clancy's. O'Neill (1850), 1903/1979; No. 477, pg. 83. Piping Pig Productions PPPCD001, Jimmy O'Brien-Moran - "Sean Reid's Favourite" (1996).

Lord Byron's poem is: HERE, and HERE, too.

~Masato