"I sang that sweet refrain" is a phrase from the last stanza of Kevin Mitchell's song

GOSFORTH'S FAIR DEMESNE

Ye tender lovers, one and all, I pray you lend an ear
To a simple tale of stirring love I mean to let you hear
And the names of those of whom I speak to you I will not tell
For all around sweet Markethill most people know them well

It being on a cool September eve, the corn was golden crowned
A gentle breeze roused through the trees, a dim glow all around
And it was the maiden fair who spoke as she clasped her true love's hand
And in an instant she cried out, Alas, I understand

That you're in love with another fair maid, prettier far than I
And so the love shines brilliant, shines brilliant in your eye
And it's oh! to think that you'd be false, that you'd bedim my eye
And with a parting kiss, alas! to you I'll say goodbye

Oh stay, oh stay, the young man cried, From you I will not go
You say I love another lass, I vow that isn't so
For had I Gosforth's castle fair and all the lands in view
From Mullybrack unto Richhill, there's none I'd wed but you

And he threw his arms around her neck and kissed her tenderly
And a cloud above fair Gosforth's heights no longer could I see
And I turned my steps towards Richhill and I sang that sweet refrain
Of the pair I left in fond embrace near Gosforth's fair demesne