Sour is under extraction. Bitter is over extraction. Or so they tell me. Or old coffee beans. That is on an espresso machine. Not sure about pour over or drip filter coffee making.

When making coffee you are actually disolving the solids and putting them into solution. Total disolved solids. and what solids you extract determines the taste of the coffee. A different grinder can change the taste. A different grind size can change the taste. A different heat level of the water can change the taste. A different flow rate can hange the taste. Pre infusion can change the taste. A different pressure can change the taste ie pour over vs pressurized espresso machine. Old vs fresh coffee can change the taste. Days since roasted can change the taste. Different levels of roast can change the taste. Of course there are different varieties of coffee beans and grown at different altitudes picked at different levels of ripeness. I'm probably forgetting more than I am remembering and I'm just a newby that probably has learned more about coffee and making coffee than I ever wanted to know in the last few months. And still know nothing. :-)