Neighbor threatening to sue over loud music.

[Ilya Schwartz]

I have a band who's been renting a row-home from me in downtown Baltimore for 4 years, their neighbor has a 97 year old mother with dementia and has been threatening to sue them and for me the noise when they practice (which is only once every two week.) The cops have been call out and said they were not breaking any ordinances. The band has noise proofed the basement as best they can, but I guess they were still not happy about it.

Now I gotten a letter from her lawyer saying if they don't stop they will sue, they've tried to ask for mediation but the neighbor just wants them to stop and if not will ask for monetary damages.  Not sure what the best course of action I should take next is.