The harp that once through Tara's halls
The soul of music shed,
Now hangs as mute on Tara's walls
As if that soul were fled. –
So sleeps the pride of former days,
So glory's thrill is o'er,
And hearts, that once beat high for praise,
Now feel that pulse no more.
No more to chiefs and ladies bright
The harp of Tara swells;
The chord alone, that breaks at night,
Its tale of ruin tells.
Thus Freedom now so seldom wakes,
The only throb she gives,
Is when some heart indignant breaks,
To show that she still lives.
Thomas Moore, from Irish Melodies
Tara is the legendary home of the ancient kings of Ireland, and the harp is the traditional instrument of the Irish bards (hence the use of harps as a slang term for the Irish, though I think no one uses it that way anymore). Once you know that, the mood as well as the direction of the poem are fairly clear: the days of glory have passed; the ancient kings honored their poets, and the poets sang their glorious deeds; and both have sunk into silence, taking the golden times with them – but an implicit hope for the future lies in the indignant, breaking hearts of the people, which show that the old ideals have not completely passed away.
What we have here is a mid-nineteenth century Irish-born poet offering a romanticized view of his nation's past in the hopes of inspiring its political future: the references at the end to Freedom, and to the indignant hearts that break, are clearly aimed at oppressive British control of its neighboring island. And yet Moore uses traditional English verse forms and vocabulary: the revival of the Celtic language would come later. But his series of lyrics on Irish themes made him a hero to the Irish struggling for independence. He was writing in the heady days of the Romantic movement, which rejected the universal and the rational in favor of (among other things) the local and the long-lost, a tendency linked to the growing nationalism of the nineteenth century. Moore was a friend of Byron, who died at a fairly young age when he went to help the Greeks fight for independence – another attempt at restoring self-determination driven by admiration for a country's past. He was close enough to Byron to be a literary executor, and he at least acquiesced in the infamous destruction of the poet's memoirs.
I took this from Moore's Irish Melodies: The Illustrated 1846 Edition, republished by Dover Publications. It's quite elaborately illustrated, with early Victorian vignettes and borders engraved on every page, so if that style appeals to you, you should definitely check it out. It seems not to be available anymore from Dover Publications, but you can still find it on Amazon. I've kept the mid-nineteenth century punctuation, though current style is lighter; I do think that omitting the comma after The chord alone would make the sense more immediately available to a current reader.