So I am playing some bass in the charity work band. A couple of tunes were in Eb, so I tuned down the E string a half step. What I noticed is it was pretty easy to play in "Eb" tuning with only that string tuned down. I can't be the person who discovered this, but I have never really heard of it. Is Drop D# a thing? Obviously drop D is, and all strings down a half step is.