I've been getting into linguistics lately and noticed the fluency aspect in terms of learned difficulty. I am fluent in two languages which adds a slight askew

I've been getting into linguistics lately and noticed the fluency aspect in terms of learned difficulty. I am fluent in two languages which adds a slight askew perspective. I find that fluency in spoken language appears to have a harmonias aspect, perhaps frequency related but also culturally harmonic. In terms of tonal sound, inflection etc. serve as probable reinforcement in terms of learned fluency.