How to make sourdough more sour

How to make sourdough more sour:

^Note the info about the rye (or other whole grains). I also would do a longer ferment of the finished dough, in the fridge. Even with my regular yeast doughs, I have them in the fridge for about 3-4 days to develop flavor.

Thank you both. There is so much to learn. My first bake was after just 1.5-2 days of starter development – it was going gangbusters so I used it early, but I didn’t give it time to mellow or, probably, build up lactic acid. The same batch has been in the fridge for a week now - maybe after I revive it and nurse it for several more days (meanwhile making pancakes from the discard, as described at Joe Pastry) it will have more character.

We never did get back to the Yukon question.