Interesting. The IV or sub-dominant, is probably the most difficult chord to improv on hearing. There are three ways to look at this. I ignore this one, look at it as a functional sub-dominant within a key. To me, within the terms of sound it's useless, sort of. More than likely or mostly, IV chords fall into the ii V realm or the I realm, regardless of musical genre.
The 2nd and 3rd view. I look at the sub-dominant, slightly askew. It all depends on it's actual function. To me, it's rarely, sub-dominant. What a word. It's either I or a function of V7. (a function of V7, what's worse?) Spelling, I get around the ambiguity, through, bass? Defines a lot of stuff. I can do what I want. To be equally ambiguous as the harmony lends or tends me. Ever so shortly.