Here are some of the more common (and controversial) flavor taints given coffee by deviations in fruit removal and drying.
Soft or Sweet Ferment. Often the sugars in the coffee fruit begin to ferment before the fruit is removed from the bean, and the fermented taste is transferred to the bean. (This inadvertent fermentation needs to be distinguished from the controlled kind of fermenting that is used to remove fruit residues from the beans during wet-processing, and which, properly conducted, does not negatively affect taste.) Soft ferment often gives a vaguely rotten taste to the cup, as though you had stuck the beans in the compost for awhile before brewing them. This rotten taste can range from a slight, not entirely unpleasant undertone, to flat out barnyard nasty.
Hard, Musty, or Mouldy Ferment. If various micro-organisms enter the coffee during inadvertent ferment the taste imparted to the affected beans can be hard, harsh, medicinal, pondy, or mouldy. Personally, I do not like hard ferment, whereas I tolerate some soft, sweet ferment. To my palate the hard or harsh tones blot out other positive flavor characteristics, whereas ferment that is sweet tends to allow other characteristics of the coffee to continue to flourish.
Earthiness. If coffee is dried on earth, rather than on dirt-free concrete, stone, brick, or wood, the coffee will pick up a distinct earth taste. Again, some consider any earthy taste whatsoever a flavor defect, whereas others enjoy earthiness and consider it an idiosyncratic delicacy. A Brazilian farmer I know has a Japanese buyer who insists that she dry coffee for him every year on earth patios to obtain the earthy tones his customers admire.
Greenness, astringency. This taint presents itself as absence of sweetness and a thin, vegetal tone to the cup. It is not a dramatic taint, but no one has anything good to say about it. It is caused by the coffee fruit having been picked too soon, before the fruit is fully ripe and sweet and the sugars fully developed in the bean. It is not a typical taint in any of the three coffees I recommend you taste, although it could turn up in the Sumatra as a background lack of sweetness.
