Analysis

1. Identify the Contrast/Relationship:
- Action: Vascoux is not exclusively (i) _______ the tenets of modern jazz.
- Result: He imbues his playing with a "pathos reminiscent of the Romantic composers." (This means he brings elements outside of modern jazz, specifically Romantic elements, into his playing.)
2. Determine the Required Meaning: If Vascoux is not exclusively following the rules (tenets) of modern jazz, it means he is not strictly adhering to them. The word in the blank should mean adhering, following, or serving.
3. Evaluate the Options:
- A. catering to: Serving or providing for a particular need or demand. (The phrase "catering to the tenets" is grammatically awkward; tenets are rules, not an audience.)
- B. undermining: Weakening or eroding. (If he were not exclusively undermining the tenets, it's confusing. The logic needs him to be not exclusively adhering to them.)
- C. debunking: Exposing the falseness of an idea. (Too strong; he's just not following them exclusively.)
- D. hewing to: Adhering strictly or conforming to. (If he is not exclusively hewing to the tenets, it means he allows other influences (like Romantic pathos) into his playing. This fits the logic perfectly.)
- E. validating: Confirming or proving true. (Irrelevant to the act of following rules.)

The word that fits the context is hewing to.