My fiance and I live in a building with a backyard that we share with our neighbor, who we'll call Constantine. Constantine frequently hosts BBQ's in the back yard, which we are very happy to attend and also help facilitate. There are 4 other apartments in our building, and there is one neighbor (we'll call him Ajax) that seems to take issue with these gatherings. This past week Ajax started an altercation with Constantine in the backyard, which pretty much killed the party. Ajax felt that 12:30 on a Saturday was late enough for people to be making noise. Keep in mind that these BBQ's may have a lot of people, but there is never any loud music, and no yelling or loud talking. I can't even hear them from our ground floor apartment when the windows are closed. There are also roughly ten other apartments that have windows onto the backyard, and no one has ever complained about the noise. How can we calm this neighbor and keep on having our awesome bbq's?
It is so hard to stay inside on a hot summer night, especially when you have a luxurious backyard. Living in close proximity to so many people often means choosing between their needs and yours. What makes for a sense of community, however, is the ability to find compromises that satisfy both parties. In the end, at least where I live in New York, unless the police can hear the noise from the front of the building, you're totally allowed to keep on rockin' out. Being technically right isn't going to help the relations of the apartment building, and might start some kind of tenant war that will ruin your summer. I think you need to offer an olive branch here, or at least some drink with sprigs of mint.
It sounds to me that your neighbor is feeling left out. Unless there are little kids up there, his Saturday midnight curfew is probably a reflection of a dwindling social life which is highlighted by the parties he hears but can't attend. I think you should invite him to the next bbq. You shouldn't post a flyer in the hallway, or yell up to him at midnight that he could join you. You should make a real honest to goodness invitation, and slip it under his door a few days in advance. Then, the day of the garden party, you should knock on his door and remind him that you would really love to share his company at the party, and does he have a bbq preference? Why go to all this trouble? Because you're actively including him in the party- which, if he takes the bait, will let him know that you aren't throwing parties to alienate him, or annoy him, and that you do try to keep the noise down to a reasonable volume. If he feels included, he won't harbor so much resentment for a normal level of neighborly noise.
Sprigs of mint, you say? Oh yes, every summer is made better by the plethora of fresh mint available. If you thought ahead, you'd already have a garden teeming with varieties of the herb. If not, you might want to go to a local farm or plant supply warehouse and buy some bushy plants of the Kentucky Colonel mint variety- the classic julep mint. Apple mint is also a great variety to freshen up drinks. When you plant mint, make sure you plant it in a garden with borders, or it'll take over all adjacent areas. I've often thought of it as a fine alternative to grass (who's going to mow the mint this week?), but few agree with me on that point. The obvious answer is to make some juleps. They're perfect for summer, and perfect for cook-outs. Now, classically, we'd mix sugar, crushed ice, bourbon, and add a few sprigs of mint for aroma. I think we need to amp it up for your party. After all, summer is about fresh options, not clinging to the classics. Let's give your bbq guests some choices, and get that stressed out neighbor loosened up with a frosty glass.
I think you should prepare several kinds of simple syrup, and put them in different small pitchers (not glasses, but vessels from which you can pour- decanters, creamers, even a gravy boat with a sizable ladle will work). Simple syrup, a solution of sugar water (generally equal parts sugar and water), is a staple of summer cocktails. Hours before the party (or even the day before), boil enough water to fill your tiny pitchers, and stir in about 3/4 that amount of sugar. Take that very sweet, hot syrup and pour it into the many containers. In one container, have fresh mint leaves (making a strong mint tea). In another, have black tea leaves and some spices (think strong chai without the latte). A third could have fresh peeled lemon or orange waiting for the syrup. Essentially, go wild with these syrups. Make them sweet and flavorful, label them, chill them for a few hours, and place them on a tray that can be taken outside to the garden party's table. A bucket of ice, and a bucket of crushed ice, should flank the syrups. Add a bottle or two of seltzer water and a few bottles of bourbon and gin, you're fancy drink bar is nearly complete. The sprigs of fresh mint should be standing in a glass of water, and a little tray of lemon and lime wedges, and other small fruits (like berries) will complete the array. Let your guests make their own drinks, and mingle with your party-killing neighbor. Soon everyone will forget about the heat and the trespasses on their quietude.
If this doesn't work, let the neighbor complain to the landlord, or move out. At least you'll know you've tried to make amends. If you give it your best shot (and a tray of prepared homemade simple syrups is a great deal of effort), that's all anyone can ask. After the neighbor explodes, or leaves, get some of your friends to move into the previously offended apartment and throw bigger parties, together. It's summer; we all need to relax a little.