The function replaces every vowel in the input string with its previous letter and every non-vowel with its next letter in the alphabet.

[CODE]:
```python
def approximate_function(s):
    vowels = "aeiou"
    result = ""
    for char in s:
        if char in vowels:
            result += chr(ord(char) - 1)
        else:
            result += chr(ord(char) + 1)
    return result
```
Now, I am going to test the function with new strings to see if the behavior is consistent.

COMMAND: PYTHON(./temp/function.py "music" "corridor" "zigzag" "temp" "netflix")