The song is an Irish tune, with words by good ol' Tom Moore. These are the lyrics I know. . .

The minstrel boy to the war has gone,
In the ranks of death, you will find him.
His father's sword he has girded on
And his wild harp slung behind him.

"Land of song," said the warrior bard
"Though all the world betray thee,
"One sword at least thy right shall guard
"And one faithful harp shall praise thee."

The minstrel fell but the foeman's chains
Could not bring his proud soul under
The harp he loved ne'er spoke again
For he tore its chords asunder.

And said "No chain shall sully thee,
"Thy soul of love and bravery.
"Thy songs were made for the pure and free
"They shall never sound in slavery."

This can be played as a slow lament or as an up-beat marching tune. The first, third, and fourth may be sung as verses, with the second as a refrain. Or, the fourth verse may be sung with the melody of the second, without the repetition of the 2nd's words. (I hope that makes sense!)