Cm7b5

Cm7b5 (also written as Cm7♭5 or Cø7) is a type of minor seventh flat fifth chord. It is built by stacking the intervals of a minor third, a flat fifth, and a minor seventh above the root note. The formula for this chord is 1 - b3 - b5 - 7. This gives it a distinctive, tense, and somewhat dissonant sound, often described as dark, mysterious, or even melancholic.

In music theory, the Cm7b5 chord serves as a dominant chord (V7) in the relative major key of E♭ major, making it functionally equivalent to an E♭7 chord. It is also used as a secondary dominant, leading to a chord a perfect fifth below it (e.g., in a progression to G7, it functions as a Cm7b5). Its unique combination of a minor seventh and a flat fifth creates a strong sense of tension that is often resolved to a more stable chord, such as a major chord or another minor chord.

This chord is popular in jazz, blues, and modern pop music. It is often used to add complexity and color to a progression. For example, it might appear in a blues progression as a substitute for a standard dominant seventh chord, or in a jazz standard to create a specific harmonic mood. The Cm7b5 is a versatile tool for composers and musicians looking to add a touch of sophistication and tension to their music.