Using the word strong to describe the amount of caffeine in a coffee is an incorrect usage of the term. Instead strong refers to a more darkly roasted coffee. A Cuban caf con leche is a variation of this Spanish drink in which nearly a quarter cup of sugar is placed underneath the grounds of a strong, finely ground espresso coffee, then drip brewed before adding heated milk to produce a strong, sweet coffee. Tangy is used to describe a coffee's taste when it has a pleasingly sharp acidic fruitiness like found in fine Costa Rican coffees. A coffee's acidity is often misunderstood.
Acidity is the true measure of a coffee's ultimate taste.
Coffee beans are composed literally of hundreds of chemical compounds. Acidity as a description of coffee, however, relates to the snapiness and life in the taste of the coffee. The full city roast of the Wild Goats' Arabian Mocha Sanani is an excellent example of a fine coffee with a tantalizing acidity that dances on one's palate. The aroma is the smell of brewed coffee while the bouquet is the smell of the coffee grounds only. A hard bean is a high-grade mountain grown coffee from Central or South America.