I have been inspecting homes and businesses for over twenty years and I have entered many areas with all sorts of different odors. In a basement that musky odor is usually caused from water or moisture penetrating the walls. If the basement is finished and there is visible mold and damage to the building materials, then you probably need to call a mold removal or mitigation company. But if there are mold odors but there is no visible mold then we recommend an Air Scrubber that can use ozone that will go out at the molecular level, killing spores in the air and penetrate the walls and kill mold down deep. It will also remove other odors like what pets and hidden bacteria can produce. Wiping down the walls with anti-viral and anti-bacterial dust wipes is also recommended in finished basements as maintenance.