Just skimmed through and maybe I missed it, but have you ever just gone over while he was playing and talked to him? As a music fan, I got to think on some level you appreciate his desire to play music (even if it sucks, we all have to start somewhere). People can be pretty easy going with a friendly conversation, "Hey I really like rock music and drumming, what are your favorite bands? Oh by the way, I live across the street and your drums are louder than my stereo so it's hard for me to enjoy my rock music, is there a way we can make this work?" Or I guess you can just keep calling the cops, local cops should keep a record of complaints and as they stock up, maybe they'd do something if it was actually against local laws after the complaints keep coming in, but if it's not against any rules, I think being friendly is the best bet.