The Astonishing Trio by Emanuel Bach

In Emanuel Bachʼs "Trio in C minor for Two Violins and Continuo ʼSanguineus and Melancholicusʼ" (Wq. 161-1), the first movement begins with an allegretto for strings, and is immediately followed by a presto for wind instruments played forte, which surprises the listener. However, these elements appear alternately thereafter. Gradually, the two come closer together, and the movement ends harmoniously.

The meaning of the title "Sanguineus and Melancholicus" is not well understood, but it can be imagined to represent the blending of two contrasting characters. The element of surprise brings to mind Haydnʼs "Surprise Symphony." Could it be that Emanuel Bach intended something similar?