Lately ive been learning some basic harmony stuff and my book says that the diminished chord is sometimes used as the vii step of the major scale.
the diminished septa- chord (vii-5-7) is built from 4 notes, one of which is not in the major scale.
For example: in C, the diminished septa chord of the vii step will be : B, D,F G#
so ive been wondering how come the use of this chord is not considered as a modulation to another tonality, when this chord seems to be out off the major or the minor scale of a certain key and which mode or scale can i use to imrpovise over this chord?