There are several options for just musty "old basement." You could put it in an enclosed container with a little container of baking soda, activated charcoal and/or epsom salts. Choose one or a combination and wait at least a week.It is a musty smell; more like the old-storage smell rather than wet basement. Curious, however, what treatment have you been using?
Thanks!
If that doesn't work, you'll have to do more than that. I can let you know what to do then, but it's a little pricey and I haven't done it myself yet. (I just got instructions on how to do it this weekend and have the products on the way.)
The wear on the bag itself is going to be a pain like Two.Time said. If you add paint to conditioner, you have to match the paint very closely or it'll show. (Try a pea size amount of paint to about a teaspoon of conditioner and mix it together.)