Complex sentence: It is, he writes, simply a parlor song in dialect, and notes that, at the time of composition, Foster was trying to bring some sort of class to the minstrel stage, but had yet to find the formula.
Split into simpler sentences: It is, he writes, simply a parlor song in dialect. Emerson explains that, at the time of composition, Foster was trying to bring some sort of class to the minstrel stage, but had yet to find the formula.