It is an arrangement of two contrasting Irish reels, "Temple Hill" and "Molly on the Shore", that presents the melodies in a variety of textures and orchestrations, giving each section of the band long stretches of thematic and counter melodic material.
[1] The two reel tunes used by Grainger can be found in the Complete Petrie Collection of Ancient Irish Music as numbers 901 and 902.
In a letter to Frederick Fennell (who would later go on to create the definitive full score edition of Grainger's Lincolnshire Posy), Grainger says that "in setting Molly on the Shore, I strove to imbue the accompanying parts that made up the harmonic texture with a melodic character not too unlike that of the underlying reel tune.
Melody seems to me to provide music with initiative, wheras [sic] rhythm appears to me to exert an enslaving influence.
For that reason I have tried to avoid regular rhythmic domination in my music - always excepting irregular rhythms, such as those of Gregorian Chant, which seem to me to make for freedom.