“Sour” dough bread isn’t necessarily sour. And not all bread made with yeast is not sour. It depends partly on the particular array of bacteria and wild yeasts that are fermenting and partly on the temperature range at which they are fermented.
I put in a shift at the Acme in Berkeley some years ago, and their bread had a wonderful flavor but was not particularly sour, even though they worked from a ferment they had been using for years, constantly refreshing. And at Wheatfields, in Lawrence, Kansas, they were making lovely, mildly sour loaves (when Thom Leonard was still the head baker.) I spent part of a shift with them, also. In both cases it took quite a while to clear the odor of sourdough from my hands. Delicious!
I used to make a seeded loaf using a poolish that was started with leftover yeast-raised dough, and it had a distinctly sour quality. I use the same process to make a whole grain loaf and it isn’t sour at all, but it is tasty. And bread dough kept overnight in the refrigerator before baking will typically develop some sour (I think @Mr.Clint advocates this, is that right?) and bakers will very commonly add quite a bit of old dough to a new batch to lend character and flavor to the new product (especially true with lean, “French” bread type doughs, but we used to do it with raised doughnuts, which are rich and sweet).