How did Johann Sebastian Bach use musical symbolism in vocal works such as the St. Matthew Passion?

Johann Sebastian Bach employed musical symbolism in vocal works like the St. Matthew Passion through two primary methods: pictorial symbolism and number symbolism.1

Pictorial Symbolism
Bach utilized a "doctrine of figures," which created musical equivalents for rhetorical figures of speech. This expressive device links specific musical gestures to the meaning of the text:1
* Rising scales are used to represent concepts such as rising from the dead.1
* Descending chromatic scales are employed to depict sorrow or a "howl of pain".1

Number Symbolism
Bach also incorporated abstract number symbolism, which can occasionally be pictorial in nature. For instance, in the St. Matthew Passion, the question "Lord, is it I?" is asked 11 times, corresponding to the 11 faithful disciples.1

While these symbolic elements are significant, scholars caution that interpreting Bach’s music through a lens of excessive numerical analysis can be taken too far. Ultimately, Bach’s ability to weave these devices into his compositions was governed by his artistic "taste"—an individual blend of judgment, skill, and imagination that distinguished his work from his contemporaries.1