I found these notes by Thomas Oram (from http://www.allmusic.com) interesting, and thought you might find it helps you understand this piece:
In the Mid-Winter Songs for chorus and orchestra, Lauridsen chose to set five poems of Robert Graves for his first choral cycle. Throughout the work Lauridsen displays the qualities that would put him at the forefront of neo-conservative choral composers, evoking the music of Benjamin Britten and Aaron Copland, while remaining perceptibly within his own conceptual framework.
Graves' classical background informs several of the poems in the work, most predominantly the first movement, "Lament for Pasiphae," in which the chorus bemoans the loss of the queen who sired the Minotaur. The pensive, foreboding movement opens with strikingly dramatic chords first from orchestra and then chorus to the words "Dying sun." At times the somewhat dissonant lyricism of the lines is reminiscent of Britten. However, Lauridsen employs little of the vaunted contrapuntal technique of the British composer, as the chorus is treated here as so often in Lauridsen's work, almost entirely homophonically; occasionally the women's voices are set in rough canon with the men's. At the halfway point and then again at the end, the "dying sun" chords return, punctuating the movement.
The brief second movement, "Like Snow," is a more light and brisk setting, in a madrigal-like vein running through Lauridsen's choral oeuvre. The frequent odd meters are often softened by Lauridsen's combination of them; for instance at the outset, two bars of five beats are followed by two of three, giving the overall effect of four syncopated bars of four beats. Colorful chords in the orchestra accompany the homophonic chorus; the orchestral interlude marking each section of text returns at the end in its most full realization.
"She Tells Her Love While Half Asleep," the third movement of the cycle, is a slow, heavily rubato setting in which the chorus is asked to declaim the text "like Gregorian chant." A repeated pair of chords from the strings is interspersed between each line of text, sung a cappella; between verses there is an extended lyric instrumental passage. The second verse is much as the first, concluding with a brooding cadence which leads smoothly into the dissonant dance that is the fourth movement, "Mid-Winter Waking." A Copland-like lyric melody in the strings serves to punctuate the choral lines. The setting smoothly shifts its meter throughout.
The final movement, "Intercession in Late October," employs warm tone clusters in the chorus against woodwind and strings which are also reminiscent of the music of Copland. The effect is one of poignancy and nostalgia, typical of the cycle as a whole, as the chorus pleads for mercy for the legendary King Midas. Lauridsen in this movement once more inserts a highly expressive instrumental interlude after which the chorus again pleads "Spare him," at first more florid and finally in unison.