According to several sources, Sean O'Neill's album "50 Irish Party Songs" contains a medley of MUSH, MUSH, TORRALIADDY/QUARE BUNGLE RYE/CUSHY BUTTERFIELD/SHAMUS O'BRIEN.

So I searched for SHAMUS O'BRIEN as a song title—also under the variant spellings SEAMUS and O'BRIAN—and found this:

From the sheet music at Duke University's Historic American Sheet Music collection

SHAMUS O'BRIEN
AN ANSWER TO NORA O'NEAL
Will S. Hays, 1867.

1. Oh! sweet is the smile of the beautiful morn,
As it peeps through the curtain of night;
And the voice of the nightingale singing his tune,
While the stars seem to smile with delight.
Old nature now lingers in silent repose,
And the sweet breath of summer is calm,
While I sit and I wonder if Shamus e'er knows
How sad and unhappy I am.

CHORUS: O, Shamus O'Brien, why don't you come home?
And you don't know how happy I'll be;
I've but one darling wish, and that is that you'd come,
And forever be happy with me.

2. I'll smile when you smile and I'll weep when you weep.
I'll give you a kiss for a kiss;
And all the fond vows that I've made you, I'll keep,
And what more can I promise than this?
Does the sea have such bright and such beautiful charms,
That your heart will not leave it for me?
Oh, why did I let you get out of my arms,
Like a bird that was caged and is free? CHORUS

3. Oh! Shamus O'Brien, I'm loving you yet,
And my heart is still trusting and kind.
It was you who first took it and can you forget,
That the love for another you'd find?
No! No! If you break it with sorrow or pain,
I'll then have a duty to do.
If you'll bring it to me, I'll mend it again,
And trust it, dear Shamus, to you. CHORUS

[A similar version of the lyrics is also found at GEST Songs of Newfoundland and Labrador, which also has a MIDI file.

[Sung by Deirdre Reilly on "Favorite Irish Ballads, Vol. 3."; by Buddy Washisname and the Other Fellers on "Flatout"; and by Marley's Ghost on "Let de Groove Rise Up".

[Instrumental versions have also been recorded by The Sons of the Pioneers on "Songs of the Prairie"; by Norman Blake on "Be Ready Boys: Appalachia to Abilene"; and by The Buckhannon Brothers on "Old Time Music: On the Air, Vol. 2".]