It must be country - it's got banjo
and harmonica.

Upbeat, catchy. Sort of a jaunty skip beat, matching the opening lyric.
The literalist in me was initially thrown (no horse-related pun intended) by the line:
she'll take no rein
the girl will always remain... public domainBecause the phrase
take the reins is usually associated with a horse's
handler taking the reins, while the horse would take the bridle.
Yeah, poetic license. I bet you're regretting that "Comments of any kind welcomed" right about now.

As clever as the title is, it feels a bit tacked on. With the emphasis on the horse analogies, I'd think a lyric like
"the one you can't tame" would be a better fit.
Good arrangement, nicely mixed, expressively sung. I liked the stereo spread of the background vocals.
Nicely done, you and Michael!
