Final answer:
A crescendo, which signifies a gradual increase in volume, typically adds growing tension to a musical passage and would be the term associated with a rise in intensity in a musical piece by Mozart.
Step-by-step explanation:
The musical term that usually adds a sense of growing tension to a musical passage, as might be heard in a composition by Mozart, is a crescendo. A crescendo occurs when the music gradually increases in volume, which can lead to a feeling of building intensity or suspense.
In a film, for example, the crescendo might underscore a scene where the protagonist senses danger, as the escalating volume heightens the audience's anticipation and emotional response. On the other hand, a diminuendo, which is the gradual decrease in volume, can also affect the mood but typically does not create tension. A cadence denotes the end of a musical phrase and doesn't inherently add tension, while an ostinato is a repetitive motif or phrase in the music, which could add tension but is not specifically about the dynamic level.