Diminished Triad

The construction of the diminished chord is that we flatten the 3rd to create a minor triad then in addition we flatten the fifth creating the diminished triad.

Well, all bass players are going to come across a few these in their days and many won't even know what they are doing. A flat fifth is also know as something rather evil. Apparently it was a sin to play at some stage of our Christian history. Black Sabbath, although Christian, played the flattened 5th often. As it was a superstition that it would conjure the devil, sabbath would cloak their instruments, their clothing and their stage with crusifixes to ward off the evil. I'm not kidding about this.

Diminished Triad: ROOT, m3, ˚5