The speaker is lying awake in a long, restless night and wishes it would change into something easier to bear. The wish is oddly specific: that night would "adjourn," as if it were a meeting that could be called to an end, and move "to an organ." The word is probably meant in the musical sense, an instrument with a deep, steady sound, though the poem leaves it open.
What the speaker wants is "a more intelligible music," something that makes sense, unlike the confusing noises or tangled thoughts of sleeplessness. The final image, bringing that music "to bed," makes it a kind of companion or lullaby, something to settle beside and finally rest with.
The mood is quiet, tired, and a little longing. There's some gentle humor in the formal word "adjourn," but underneath it is a plain human wish for comfort. The poem is very short, and the brief lines and gaps feel like the thin, broken stretches of a night spent waiting for sleep.