When I was learning theory/harmony, we'd consider a perfect fourth as a dissonant interval. It kind of bugged me because the teacher wouldn't really give a good explanation why. I've come to accept it, but I still think fourths sound really awesome. PARALLEL FOURTHS (I'm going to hell!). It's not the kind of thing that would fit in classical harmony, but it doesn't create a black hole, so I'll play all the fourths I want to.It's late, and I'm kind of posting to myself... anyways, C-F to me instantly shouts out subdominant-tonic because of how I was taught it for the past 10 years. What if we had a 15 key piano with all these alien intervals? I'd love to see how many people would go absolutely insane