The aspect that I have the most expertise in is lyrics/lyricism. There are some truths to such things as frequencies and those aspects you mentioned too though. The aspect I mainly focus on is lyricism and the MC aspects. It is actually quite fascinating, I've had conversations with artists where I've said in your life have you " " and they were like yeah, shytt how you know that??? Lol. It's nothing mystic or supernatural, it's just a deep understanding of lyricism/content/Hip Hop and relateability and what kind of people relate to different songs/artists. It's often dependent on the circumstances and situations of their lives, for instance Pac is so popular because he was so diverse content wise. People felt like he was speaking for them, he also had that touch of craziness/care free/going all out type shyt, which for some people is the idealism and fantasy but for others is the reality of their lives. There's almost 2 types of Pac fans, the 1's who cling mainly to the Thug aspect, a lot of those unfortunately are more in love with the image than the music then there's the 1's who have a fuller more complete grasp of the body of work. Because Pac spoke on such everyday/hood but still deep issues. There is also the better days philosophy Pac uses, he puts that in his music partly to inject hope to his listeners, that gives you a subtle feeling of hope and that things can get better even in a state of seeming hopelessness. So a lot of people who have REALLY been through some shyt in their life, whether personal problems or in the streets can relate to Pac due to this. He spoke for those people.
I'm happy to give it a go at least, won't always be accurate but there are certainly common factors found that are usually correct. There's always exceptions but there's common themes, I've dealt with so many Hip Hop heads, artists, producers etc it's almost like 2nd nature. A friend of mine is very knowledge on the frequency aspect of it, much more than me, infact he put me on to all that shyt many many years ago, I later did my own research and discovered there is truth to it. He's a producer too so he understands that side, in regards to a mix too as he's an engineer. Very wise, interesting fascinating person, if he posted here you'd see what I'm talking about. It's like reggae, reggae has the capability to uplift and even be healing, therapeutically, obviously certain types of reggae lol. But it's remarkable, it's deeper than there's even time to explain. Hip Hop can be like... often be rebellious, like give you fight and determination rather than letting you sink into deeper depression like some music from other genres, that's 1 of the reason I love Hip Hop, it's positive and strong in that sense.
In terms of how much you know about the listener, it's usually the artists they listen too and favourite songs etc. Sometimes ask personal questions due to curiosity but can be kept music. It's normally accurate yes to be honest, I don't remember a case of it not having any truth or merits to it.