"Our moods do not believe in each other." Emerson
Forward to Book of Moments
Lyrics are "moments" insofar as they pause to sum up a motive. They are designed to express and evoke a unified attitude towards some situation more or less explicitly implied.
In one's moments, one is absolute. Though there may not be current names for some of them, all moments are as though capitalized: Delight, Promise, Victory, Regret, Apprehension, Arrival, Crossing, Departure, Loneliness, Sorrow, Despair, etc. in summing up a past, they ambiguously contain a not yet unfolded future (in fact, a future that may forever remain in the state of sheer implication, as with the remote possibilities for good or evil that jurists have to consider, when speculating about the constitutionality of a new law).
Ideally, perhaps, one should break down a motive into many different kinds of moment. For instance, a poet might make it a rule that whatever he happened to vilify in one lyric, he would glorify in another, that whatever he wept about this time he would laugh about the next, etc. The ideal lyricist would probably speak through as many shifting personalities as the ideal dramatists.
But in practice, regardless of the many moods a person experiences in a day, only some of them lend themselves to his particular ways of expression. He skimps on the multiplication and diversifications of moments, if only through inability to do otherwise.
Day after day, year after year, he may have a fairly fixed attitude towards something, and may in fact build the whole logic of his life in accordance with this attitude--yet of a sudden, for a spell, he may be invaded by some quite different attitude, and this irruption may be the element that, for him, falls into the pattern of a momentary poem.
Some of the past moments, here recovered from my records of dead selves (a selection extending back as far as adolescence) are doctrinal ("propagandistic," "didactic"). A poem is no less moody, through having turned from sensibility to ideation, though current literary views often conceal this fact....Ideally, here again, the complete lyricist would not shun the didactic; he would love ideas at least as strongly as sensations, and preferably more; but he would range among them "moodily," and would never proffer a candidate for canonization without also attempting to write as good a brief as possible for the advocatus diaboli. Only by a maximum of such free ranging could poetry best help to keep us free.