The mmM7♭5 chord, also known as the minor major seventh flat five chord, is a complex and intriguing chord that offers a unique blend of tension and resolution. This chord consists of a minor triad with a raised seventh and a flattened fifth. Notably, the minor major seventh aspect gives this chord its distinctive sinister or mysterious sound, while the flattened fifth adds dissonance. In terms of construction, the chord uses the formula: root, minor third, diminished fifth, and major seventh. For guitar players, practising this chord in several positions will be beneficial to fully grasp its harmonics and applications. Often used in jazz and avant-garde music, this chord can add a unique atmospheric layer to compositions or improvisations.