Music is a most common way for people to express their feeling, same like the poem and writing, it's reflected what your thoughts or feels. With a bad emotion can't write a joyful article; sometime we can call this is our “mood”.
The play list in your phone or laptop might tell you what kind of characters you really are. You can't enjoy the sad song when you feel happy, you needs something can reflect your happiness from you current emotion.
It's a reflection of your personality from the play list. Positive people like to listen the song or music which fast tempo, well negative people whould like to enjoy in more slower and low tempo.
It's hard to observe a person from what you just looks at them. People may act according of thier roles, but a personality is from their inside, what is the origin of their thought. It's a base of them.
Sometime, it's very hard to speak out what you feel now. Some moment just indescribable, you can't find out a single to describ it. But music can simply release it; the emotion, feeling and thoughts.
Talkative people which like to listen pop-song, rock song, it create the topic for them to others. Sensetive people which more likely to listen to soft music, it clear their mindset and let them immerse in their world.
Just like some people would prefer for clubing song or heavy matel, those are strong tempo help them to release their stress or to have a moment run out from the reality.
So that, to know whether the person has a same taste with you or not, try to see what kind of song they like to listen.