Sentence:  In skillful fugues the heightening tension of contrapuntal development finds confirmation in peaks and <WSD>underpoints</WSD>, dissonance quotient, and expansion or compression of tessitura, as well as other less direct sources of stress such as the largely intellectual pleasure of increasingly sophisticated and arcane manipulations. 
Meaning of the word marked with <WSD> tags:  The lowest intensity point of a diminuendo that is followed by an increase in volume and intensity.