Hi Vinyrd Skynyrd.
As soon as you pull the cork on a bottle, you’re exposing the wine to oxygen. Oxygen and warm temperatures are spoilage ingredients for all foods, including wine (which is why we usually cover that leftover quiche in plastic wrap and pop it into the fridge).
When I have a leftover half bottle, I usually pour it into a clean beer bottle and cork it or float some wine preserving gas over the wine before I pop the wine into the fridge.
With air exposure, wine aromas and flavors decrease. This degradation is most quickly noticed in delicate whites. Robust reds, which have a lot of aromas and flavors to begin with, last longer.
As for vinegar, that’s caused by acetobacter. In the presence of oxygen, this bacteria converts alcohol into acetic acid. In the winery, sanitation and SO2 usually keep acetobacter from rearing its ugly head.
And Walt’s sour rose? As the ripe fruit aromas and flavors decreased, the wine’s acidity became more obvious.