IMO this is part of high density living, be it apartment, condo, or whatever. Unless it's a seriously repetitive problem, you both pay to live and enjoy yourselves there. Barring any specific HOA violations, it needs to be resolved between the two of you. It sounds like young people next door. If they're having people over and your knocking on his door @ 8pm on a Friday, you're going to embarrass them and potentially make the problem worse. If its 10pm on a wednesday thats different, but again choose your battles wisely.
I absolutely loathe the idea of having this "neighbor" and also of being that "neighbor". These are some of the many reasons I have little to no interest in the hip "urban" life. If i'm paying $300,000 for a place, you can bet your rear end I'm doing whatever the heck I want. That's why my place is on a multi acre lot
I even shoot guns on my property, but do so infrequently to be a respectful neighbor--everyone else around here bought homes for privacey, peace and QUIET, too. But when we have parties, out come the DJ speakers and 100watt amplifiers until at least 11-midnight. Again, maybe twice a year and neighbors are of course invited (they're all much older and don't come, but it serves to alert them it's "party time")