Here’s another installment concerning ‘half-diminished” chords. Remember that “half-diminished” and “minor-seventh (flat5)” are synonymous.
So far we have used three-fingered shapes combined with an open string to produce the four-note “minor-seventh (flat5)” sound. This time let’s find a four-fingered version of it. We’ll get to the theory eventually.
If you are familiar with my arrangement of “Brother, Can You Spare a Dime” (from my Great American Songbook CD and Book), you already know a B half-diminished chord. In that tune, I use it as a II chord in a II-V-I chord progression in the key of A-minor. It has an angst-producing sound, perfect for accompanying the lyric of that song.
B half-diminished is a very common chord on the guitar because it is so easy and sounds so good! If you don’t already know it, here’s the non-theoretical method of producing it:
Play a normal, first-position D chord. Move this ENTIRE SHAPE one STRING toward the bass (NOT one fret up the neck!), so you are fretting the second, third, and fourth strings. Add your little finger on the first string, 3rd fret. This combination of notes on the four treble strings is a full diminished seventh chord (the melodrama, tie-Nell-to-the-tracks chord).
To produce the neighboring half-diminished chord, move this entire diminished-seventh shape one more string toward the bass, so you are fretting the fifth through second strings at the 2nd and 3rd frets. Voila – a B half-diminished chord, using the four inner strings.
Follow this Bm7(flat5) with an E7, then an Am (the II-V-I mentioned above). That is an intrinsic chord progression in “Brother.”