We can feel your pain...
We have 2 sets of neighbors with dogs. The first are so very friendly and keep their dogs within their fenced property. We never had a moments problem with them UNTIL their neighbor moved in with 2 large mean rottweilers. They had a pen for them but after 4pm and weekends when our Animal control closed, they would let them out to have a run...through all our yards and stirred up our neighbors dogs as well. After numerous complaints from many, the animal control paid them a visit and must have scared them enough that they do not let them roam anymore.
BUT, they did bark - all day and all night which caused our good neighbors dogs to reply...We purchased a Bark Silencer that will hang on a tree or pole that you can aim in the dogs direction. When the dog barks, it sends out an ultrasonic sound that irritates the dog, when the dog stops barking, the sound stops thus training the dog not to bark. There are many on the market so do research to determine the cost with the distance you need. Our device will pick up the bark up to 75' away and was just under $100. It has AC/DC compatability. What we did was talk to our neighbors and split the cost to put it on their property, aimed at their neighbors...thus stopping the problem.
Regarding the drum issue...the only thing I would think you could do is contact your county councilman. Maybe there is a noise ordinance that they are in violation. Most of this go into affect during night hours which vary from area to area. In discussions with him, state the previous issues and your resolvement to those issues - i.e. the fence and expantion of your parking. This will provide him (her) proof that you have gone to extreme measures with this neighbor but that this issue is beyond your ablity to resolve. Wish you luck with this one!