I have gone on about how great Bushwalking's No Enter is. Today, shuffle play threw the title track at me and now I'm obsessed again. When you listen, pay attention around 5:30 - there is an absolutely perfect wrong note at 5:44. You can't miss it. It is sour in exactly the right way.
Here are a couple recorded examples of my own attempts at intentional sourness (or microtonal guitar if you prefer) from the past 25 years:
Kohoutek (at the end at least)
I need to do more with this particular mood. I'm feeling it.