A speaker addresses a person for various reasons. For example, s/he may see that the listener is distracted and s/he may want the addressee to focus more on what s/he has to say. Moreover, it can happen in the middle of a speech, because what will follow is really important and s/he feels the need to underline it by asking for more attention from the listeners. Furthermore, the speaker may address a person because s/he may want to talk specifically to this person about something or in order to give him/her the stand.
So, from all the above, it could be concluded that the basic request of the speaker when s/he addresses a person is to grab the listener's attention.
The author provides an inference context clue to help determine the meaning of the word heavy. The phrase “erupting like great beasts” helps the reader infer that the “heavy electronic beats” coming from basements are quite forceful.
