For myself, I find a synergy between verse an tune; frequently one or the other will "take command" and "demand" a particular direction.

Once it has been "hacked out"... the revision, the refining, the distillation process may extend over years....put away and picked up again later...."solutions" come when occupied with something else...(generally, mowing the lawn.)

I like Robert Frost's explaination regarding his poetry...."the pleasure of taking pains."