C7b5

— About this chord

C7♭5 (1-3-♭5-♭7) lowers the 5th of a dominant seventh for a hollow, whole-tone-tinged tension that sits between dominant and diminished color. A favorite in bebop and cool-jazz reharmonizations, it's frequently used as a tritone-substitute-adjacent voicing or to add a wry, off-kilter edge to a static dominant vamp. On guitar it's easy to grip as a compact open-ish shape near the nut, or transposed to a low-string voicing for a darker register further up the neck. Common in ii-V-i turnarounds and as a chromatic passing chord between a major chord and its relative dominant. Also searched as Cdom7b5 or C7 flat 5.