
Shalshelet

The Shalshelet (Hebrew: ) is a cantillation mark found in the Torah. It is one of the rarest used, occurring just four times in the entire Torah, in Genesis 19:16, 24:12, and 39:8, and in Leviticus 8:23. The four words accented with the shalshelet mark all occur at the beginning of the verse.
The Hebrew word שַׁלְשֶׁ֓לֶת translates into English as "chain". This shows the connection of the worlds by the links of a chain. The symbolism of the Shalshelet is that the subject of the story is wrestling with his inner demons and is undergoing some hesitation in his actions.
It is rendered musically by a long and elaborate string of notes, giving a strong emphasis to the word on which it occurs.
Purpose.
The Shalshelet mark is said to be used for various purposes:
Grammatically it is equivalent to "segolta", but is never preceded by a conjunctive accent or a disjunctive of a lower class. It is thus related to "segolta" in the same way as "Zakef gadol" is related to "zakef katan", or "Yetiv" to "Pashta".
Total occurrences.
The shalshelet note occurs a total of 7 times in Tanakh outside of the Sifrei Emet. They are:
Additionally, the note occurs 39 times in Psalms, Proverbs, and Job.
Melody.
The Shalshelet has a melody similar to that of 3 Pazers. 
According to Chabad tradition, it is equivalent to 2 Pazers and one Tlisha Gedolah. Rabbi Stolik of Chabad Caltech disputes this "Chabad" tradition.
It is approximately 30 notes, though this number varies depending on the word on which it is used.