1) Explanation

Let's break down the sentence to understand the context and the meaning required for the blank:
- "As my musical ability began to $\qquad$ I logged my progress in my journal,"
- The blank describes a change in musical ability. "Logged my progress" suggests a positive change or development. If you're logging progress, it implies improvement.
- "describing the mellifluous melodies and harmonies that seemed to spontaneously flow from my fingertips."
- The phrase "mellifluous melodies and harmonies that seemed to spontaneously flow from my fingertips" clearly indicates that the musical ability is getting better or more refined and easier to produce. "Mellifluous" means sweet-sounding or pleasant to hear. This strongly supports the idea of improvement.

Let's evaluate the given options:
- A. wither: To fall into decay or decline; fade. This implies a decrease or worsening, which contradicts "logged my progress" and "mellifluous melodies."
- B. advance: To make progress or move forward in a skillful way. This perfectly fits "logged my progress" and the description of effortless, beautiful music.
- C. deteriorate: To become progressively worse. This implies a decrease or worsening, contradicting the positive context.

- D. erupt: To break out or burst forth suddenly. While music might "erupt," this doesn't specifically describe the ability itself improving or declining; it describes the act of playing. It doesn't fit with "logged my progress" in terms of skill development.
- E. subside: To become less intense, severe, or active. This implies a decrease, which contradicts the positive context.
- F. improve: To make or become better. This is a direct synonym for "advance" and clearly fits "logged my progress" and the description of "mellifluous melodies."

Conclusion:

The context provided by "logged my progress" and the description of "mellifluous melodies and harmonies that seemed to spontaneously flow" strongly indicate that the musical ability was increasing or getting better. Both "advance" and "improve" fit this meaning perfectly.

The correct answers are B. advance and F. improve.