Perfect fourth/Perfect force.

Apart from this exhilirating concert I was privileged to hear [Which, apparently, you are not - since the video for some reason won't come up. So you'll have to take my word for it: it was hilarious! Both my nephews at our old, totally out-of-tune piano, the younger one messing about while the older one, totally absorbed, plays perfect fourths over and over again, in different places on the piano keys, mindful to correct himself when accidentally hitting a third of fifth...]
I forgot to mention that I have been asked to fill in for my colleague, the music teacher, who has been incapacitated by fickle Fate for a good while. Which means that besides worrying about her health I now also get to worry about all the stuff I get asked to do. You know, small, insignificant, easy-peasy tasks like overseeing/rehearsing/putting together the school musical. Or like taking over as conductor of her church choir. Stuff like that. I am simply thrilled at the prospect. (Mostly, I am thrilled that I have classes at university on School Mass days, or they would have delegated all musical organization/presentation of those to me as well.)

I am not overwhelmed at all.