A chord which is also referred to as minor seventh flat 5 (m7b5), since it is exactly that... a minor seventh with a flat fifth. The tones present in the chord are the root, a flat third, a flat fifth, and a flat seventh (this also makes it a diminished triad with a flat seventh stuck at the end), and if the seventh were flatted once again, it would be a fully-diminished seventh. In strictly diatonic music, one would play the half-diminished seventh off of the seventh tone in a major key, or the second tone in a minor key. If you're soloing and another instrument is playing a half-diminished seventh, you can get away with playing the minor blues scale, locrian mode, or altered scale of the chord's tonic note. This chord resolves quite happily to the dominant seventh two whole steps down (eg, Bm7b5 -> G7).

We now deviate from theory to spell out a few half-diminished seventh chords:

  • Am7b5 contains the notes A C Eb G
  • Fm7b5 contains the notes F Ab Cb Eb
  • Cm7b5 contains the notes C Eb Gb Bb
If you happen to play the guitar, here are the CAGED forms of the chord on the guitar neck:


 Cm7b5  Am7b5  Gm7b5  Em7b5  Dm7b5
By sliding those shapes around and using this handy information, you can form any inversion of a half-diminished seventh you damn well please.