The diminished scale is a symmetric scale widely used in jazz that consists of eight notes. Your study will allow you, among other things, to sing on the versatile diminished seventh chord that I have already explained to you, or on a dominant chord.
The diminished scale is characterized because it is constructed by means of intervals of tone and halftone in a regular way. Thus, it can be presented in two different ways:
-ST-T
-T-ST