The show’s songs are an enjoyable mix of styles and moods, from the irreverent setup “Populism Yea Yea” and “Illness as Metaphor” where we get a Susan Sontag reference to a sobering “Ten Little Indians” and heartrending “The Great Compromise” (the latter sung so touchingly by Nashville newcomer Savanna Garnick, whose voice is the welcome-to-the-ear audial equivalent of clear water cascading gently and evenly down mountain rocks).The key newcomer is Savanna Garnick, cast as Rachel Jackson, the put-upon and publicly pilloried first lady-elect who dies before her husband can take the oath of office. Garnick brings a sultry sense of melancholy to the role, which she plays well, counter to all the parody. She sings sensitively, too.