tangy sourdough bread

I have a very active starter that I purchased from KA Flour. It lives in the fridge until I'm ready to bake but always rises quickly when I bring it out and feed it. It makes great bread just not very sour. I have been doing some reading here on how to make breads more sour and one of the things I'm going to try is to just let the starter live on the counter and feed daily and see if that helps but I've also come across a suggestion to use sour salt to get a more sour flavor. Does anyone have any experience with this? Does it make for a more sour bread?

Thanks!