Q: Is the wording in this song ok? One of my favorite songs is Ain't no mountain high enough.
The chorus is this: 
Oh baby there ain't no mountain high enough,
Ain't no valley low enough,
Ain't no river wide enough
To keep me from getting to you babe

I am a native German, and I am always struggling: can a valley be too low? I am used to say a valley is too deep. This applies to a river as well. A sea or a lake might be wide, but what hinders me crossing a river is its deepness or wilderness or maybe it is too big. I know it is lyrics, so there is a lot of freedom in the wording, but I am wondering how an English native would say it and if the imaging is correct (wide river, low valley)?
Personally I would have written:
Oh baby there ain't no mountain high enough,
Ain't no valley deep enough,
Ain't no river wild enough
To keep me from getting to you babe


A: Low Valley
Given that the first line uses high, I think the 2nd line is using low as its antonym. Per Google Ngram Viewer, it does seem like low valley is not as common as deep valley (although not nonexistant):

I think usage of "low" versus "deep" also lends the song some additional benefits. It's easier to modulate "low" (and more fun) than deep.
Wide River
I think the concept of a river's width prohibiting crossing is valid. Ceteris Paribus, River A will be more difficult to cross than River B if River A is wide.
Google Ngrams seems to bear this out. In fact, for the 19th Century, "wide river" was more common than the other variants, and is still pretty common:

In terms of how "wild" sounds: I like imagery, but I think ultimately "wide" fits better into the rest of the chorus (physical distance won't prohibit me from getting to you). Also, depending on how you sing it, "wild" might end up sounding like "wide" anyways.

A: I think you'd get more interesting answers if you asked this question on https://music.stackexchange.com, but here's my take on it.
First, thanks for posting an alternative, because reading it made it clearer to me why the original is the way it is.
how to make the same note sound different
Think about how the lines are sung, and where the emphasis is placed:


*

*Ain't no moun-tain high__ e-nough 

*Ain't no val   -  ley   low___ e-nough


"High" and "Low" are the key words on each line. The first contrast is obviously between "high" and "low", but the second contrast is more subtle: "high" contains a narrow vowel (tongue back), and "low" contains a broad one (tongue flat).
The interesting thing is that even though both are actually the same note, "high" sounds like a higher note than "low" - another contrast.  It may surprise you to know that both of these lines are sung to the exact same melody - it's only the change of vowel on the emphasised word that makes them sound different.
(the opposite of this effect is frequently used in choral signing, with high-pitced narrow-vowel replaced with broad vowels to ease vocal strain: "leaf" becomes "laugh", but thanks to the higher pitch, the audience hears "leaf")
If you use "deep", as in your alternative, that's a narrow vowel, just as in "wide". By putting two narrow vowels in each line you end up with a more repetitive sounding melody - it's now very obvious that the two lines are a repeated phrase.
