What is a half diminished chord?

A half diminished chord is a four-note chord consisting of a root note, a minor third, a diminished fifth, and a minor seventh. It is also known as a minor seventh flat five chord (m7b5).

The half diminished chord is commonly used in jazz music and is often used in chord progressions where it functions as a passing chord between a diminished chord and a minor chord.

The symbol for a half diminished chord is a circle with a diagonal line through it followed by a 7 (ø7). For example, the half diminished chord based on the root note of C would be written as Cø7.

The half diminished chord has a slightly dissonant and unresolved sound due to the diminished fifth interval, which creates tension and a desire to resolve. This makes it a useful chord for creating tension and interest in music.