It’s surprisingly hard to dig up information on the diminished scale. Remarkably, The Alfred Complete Book of Scales, Chords and Arpeggios makes no mention of them. I don’t know why the scale is neglected. Maybe it’s not traditionally used very much in classical music. But the diminished scale is very important to Bebop jazz, so I really wanted to learn it in all keys.
For a couple of years, I used fingerings that I came up with which seemed like the best ones to me at the time. (Since there are three distinct scales, I’ll describe them as C, Db, and D). For C and D, I used tetrachords, with thumbs together on F and B. For Db, I used 2312123 for the RH and 32132121 for the LH (Notice how the thumbs aren’t paired). OK, so these fingerings get the job done, but they’re not elegant. I didn’t fully understand what I was doing, but in my impatience to get down to work I picked one thing and went with it.
As I progressed, I got more curious and dug a bit deeper into the internet. I found that there were two main ways of fingering diminished scales:
1. Thumb over tetrachords – an advanced and elegant technique that I’ll tackle in the future.
2. the ‘123 123 12’ technique where thumbs always play white keys, and they are paired (left and right thumbs play at the same time when playing the scale in unison an octave apart).
Here’s the scale with this fingering indicated, notice how thumbs go together:
But here’s the cool part, which makes me REALLY LOVE this fingering!! If you look carefully at the C diminished fingering, the thumbs spell out an F major triad. Likewise, for the Db dim fingering, the thumbs spell out a C major triad. For the D dim fingering, the thumbs spell out a G major triad.
This simple trick made diminished scales seem so much more logical. I don’t have the diminished scales internalized this new way yet, but now they are a lot easier, and it’s beginning to show in my improv. For instance, if I see an E-flat-diminished chord in a song, I just go “Oh, that’s the one where my thumbs outline F major.” And then the fingering falls into place really quickly.
I came up with this myself to the best of my knowledge, so I hope it’s useful to you.