What's Up With All The Shouting (er Singing) at 8pm Everynight?

It appears that some residents have noticed some strange behavior throughout the weeks:

What’s up with the flashing lights, music in the Sloop at 8:00 pm?

Another reader writes:

I was wondering if you or any readers could solve a small mystery!  Have you heard the people screaming and shouting from their windows in the neighborhood at 8pm every night?  Do you know why? 

I've heard about folks in Spain doing something similar as a salute to health care workers, but I haven't been able to track down what the meaning is here.

Well it started on Saturday night and was a city wide thing (via ABC7 Chicago):


The act of unity has continued each night.  One reader sent us this video:

Most of the daily organizing is going on at HSL on Facebook here.  NBC 5 also has an update:

Another massive sing-along - this time to two iconic Queen songs - was set to take place across Chicago Friday as Illinois' stay-at-home order remains in place amid the coronavirus pandemic. 

This week's sing-along was scheduled to start at 8 p.m. on March 27, organizers say, inviting everyone to sing "We Will Rock You" and "We Are The Champions."

(Hat tip: JN, AH, BS!)