Augmented Triad: An augmented triad consists of three notes stacked two whole steps apart. It has an unsettling sound similar to diminished seventh chords.
Secondary Dominant Chord: A secondary dominant chord is a non-diatonic chord that functions as the dominant of another chord within a key. Diminished sevenths can be used as secondary dominants for added harmonic interest.
Enharmonic Equivalents: Enharmonic equivalents are different notations for the same pitch. Diminished seventh chords can have enharmonic equivalents, meaning they can be written in multiple ways while sounding the same.