First off, I would like to say thanks to Stephen Pale of the Neverends for this hint. Stephen Pale is an excellent guitarist, and has a great handle on music theory. His band is starting to get some gigs in the New Milford, New Jersey area, and you might want to check them out. =]
The Minor 7 Flat 5 (m7b5) chord, also known as the Half Diminished Seventh chord is a chord frequently used in jazz, mostly as the ii portion for the ii-V7-i progression in a minor scale, serving as a predominant of sorts.
Now for those who do not know what a Minor 7 Flat 5 looks like, it’s a diminished chord plus a minor seventh. A diminished chord is a minor chord, with the fifth of the triad flatted. For example, C minor is formed by C-Eb-G. A C diminished chord is formed by C-Eb-Gb, instead of a G. The minor seventh is the same seventh you would play on a Cm7, which is the Bb.
The quickest way to form the chord would be as such. We will use Cm7b5 as the example.
1. Start with a C.
2. Use the next note as if you were forming the minor chord triad. In this case, an Eb, as a Cm triad is C-Eb-G.
3. Starting with the note in step 2 (Eb for this example), create its minor chord triad. Ebm would be formed as Eb-Gb-Bb.
4. Voila, your Cm7b5 chord is C-Eb-Gb-Bb.
Personally, I feel this makes it easier to think of the chord on the fly when playing piano. Your left hand would play the first note, then your right hand would play the minor chord in step 3. A Cm7b5 is the equivalent of Ebm/C, which may make it easier for some folks to visualize. A Bm7b5 would be Dm/B. An Am7b5 would be a Cm/A, etc.
So hopefully this makes for a good mnemonic device. It should help you make those minor scale 2-5-1′s a little quicker. =]
More to come.