Get a Lampeberger. They are sold at cigar stores because they do such a good job a cleaning the air. Another webmaster who smokes cigars recommended it and it's great for dog smells. I get my oil here:
http://www.maisonbouquet.com/
Mix it with 91% (make sure it's *91%*) rubbing alcohol - depending on the scent I do half/half or 1/3 oil, 2/3 alcohol.
If it's truly musty a dehumidifier will work wonders. Get one that you can channel outside if it's really damp. I had one in my basement in the burbs and they turn off when all the moisture is out of the air - mine didn't turn off in 5 years, lol.