This request falls into the realm of the surreal and imaginative, as it's not based on any real-world physics or measurable phenomena. Therefore, the "calibration" and the "whispering square moon" are entirely up to your interpretation and the story you want to tell!

Here are a few ways we can approach this "calibration," each leading to a different kind of narrative or feeling:

**Option 1: The Metaphorical Calibration (Focus on Intention and Emotion)**

If the invisible banana represents something abstract (like hope, a secret, or a feeling), then calibrating means aligning it with something that evokes the desired response.

*   **Calibration Method:** Gently infuse the invisible banana with a sense of **wonder**. Imagine holding it, feeling its potential, and focusing your intention on the ethereal. Think about the quiet hush before a revelation, the anticipation of something magical.
*   **Why it works:** The square moon, in this context, might represent a cosmic observer or a manifestation of collective dreams. When the invisible banana (hope, a secret) is infused with pure wonder, it resonates with the subtle frequencies of this observer, causing it to "whisper" its agreement or acknowledge the connection.
*   **What the whisper might sound like:** A faint hum, a rustling of stardust, a barely audible sigh of understanding. It might convey a feeling of "yes," or a gentle encouragement.

**Option 2: The Conceptual Calibration (Focus on Logic and Paradox)**

If we treat this as a playfully absurd logical puzzle, the calibration involves finding the specific, albeit nonsensical, conditions that trigger the event.

*   **Calibration Method:** We need to find the **perfect ratio of non-existence to unseen potential**.
    *   **Step 1: Measure the "invisibility."** Imagine a meter that measures how truly unperceived something is. We need to dial this up until it's almost infinite.
    *   **Step 2: Quantify the "banana-ness."** This is trickier. Perhaps it's about the *idea* of a banana, its inherent "banana-ness," stripped of all physical attributes. We need to find the pure essence of a banana, existing only in concept.
    *   **Step 3: Introduce the "squareness" to the moon.** The moon's squareness is a deviation from the norm. The banana's calibration must somehow mirror or interact with this anomaly. Perhaps it needs to be calibrated to the *degree of imperfect geometry*.
    *   **Step 4: The Whispering Trigger:** Once the banana is calibrated to possess a flawless degree of imagined immateriality and a perfect alignment with the moon's geometric anomaly, the moon's very structure will vibrate with an unheard frequency, translating into a whisper of acknowledgment.
*   **Why it works:** In this nonsensical logic, the extreme paradox of a perfectly calibrated "nothing" interacting with a geometrically "wrong" celestial body creates a feedback loop that results in a uniquely subtle communication.
*   **What the whisper might sound like:** A series of clicks that don't quite form words, the echo of a forgotten question, or perhaps a static hum that rearranges itself into a single, unintelligible syllable.

**Option 3: The Artistic Calibration (Focus on Sensory Experience and Imagination)**

This is about the creative act of bringing the invisible into being and conjuring the whispered moon.

*   **Calibration Method:**
    *   **Visualize the Invisible Banana:** Imagine its form, its texture (even though it's invisible), its scent (even though it has no smell). Give it a subtle presence in your mind's eye.
    *   **Sculpt its "Un-Existence":** Use your imagination to "shape" its invisibility. Is it a void, a shimmering absence, or something more present in its lack of presence?
    *   **Tune the Square Moon:** Project an image of the square moon. Now, listen. Not with your ears, but with your inner sense. What does a square moon *sound like* in its silence? Is it a hum, a vibration, a felt pressure?
    *   **The Resonance:** Slowly, subtly, bring the imagined feeling of the invisible banana into harmony with the imagined sound of the square moon. Perhaps the banana needs to be tilted at a specific, unheard angle, or its "energy" needs to be focused through a single point of pure imagination. When these two abstract elements align in your perception, the square moon will let out its whisper.
*   **Why it works:** This is about the power of shared imagination. You are the conduit through which this surreal event occurs. By engaging your senses and creatively interpreting the prompt, you make it "real" in the context of your mind.
*   **What the whisper might sound like:** A soft, almost melodic sigh, the sound of light bending, or a whispered secret passed on the wind. It might be a single word, spoken in a language you almost understand.

**To "calibrate" it for your specific purpose, consider:**

*   **What is the *feeling* you want to evoke?**
*   **What is the *story* you want to tell?**
*   **What is the *meaning* of the invisible banana and the square moon in your context?**

Let me know which approach resonates with you, or if you have a specific idea in mind, and we can refine the calibration further!
