The syllables "Fa", "Sol", "La", and "Mi" repeated at the beginning of the song, are used in a form of singing called "Shaped Note Singing" or "Sacred Harp Singing", in which shaped noteheads are used to help singers learn their parts quickly by sight. "The notation, introduced in late 18th century England, became a popular teaching device in American singing schools." This is what it sounded like:
It is typical to begin a song by having all singers learn their part by singing the syllable associated with each note, and then sing the words to the song on the second time around. The Pottsfield singers follow this practice.
The biggest deviation in style from normal shaped note singing is that shaped note singing is almost always acapella, (Pottsfield's version features a string quartet).
Another hidden reference is the track title: "Pottsfield CM". Many Sacred Harp songs are referred to by their tune name (often a place-name) and their metre. CM is short for "Common Metre", which is (surprise) the most common metre in Sacred Harp songbooks. Hence, "Pottsfield" is the tune name, and they assert that the metre is the "Common Metre".
However, Pottsfield does not exactly match Common Metre. Common Metre has 4 iambic lines, with alternating lengths of 8 and 6 syllables. Pottsfield follows an approximate 8-6-7-7 or 8-6-6-7 syllable-per-line pattern. (You can still sing these words to CM songs such as "Amazing Grace" or "The Pokemon Theme", and vice-versa).
Unofficial shaped-note sheet music for Pottsfield CM is available here.
1. O hie thee forth o'er golden mead
Yon is the maypole set
A ribbon to wind thy soul,
And to bind love to thy breast
2. From flesh removed our chalk footfall
Tempers this holy ground
Where timeless spirits meet
'round the heart of Pottsfield town.
- The somewhat macabre nature of Pottsfield and its citizens is given away in the first three lines of this song. These lines are not heard during the episode.