The diminished scale as diminished chord + four dominant roots

Play a diminished seventh chord and lower any one note by a half step, leaving the other three alone. The result is a dominant seventh whose root is the note you lowered. From C diminished: lower C to get B7, E-flat to get D7, F-sharp to get F7, and A to get A-flat 7. From B-flat diminished you get A7, C7, E-flat 7 and F-sharp 7 (the captions say F7 here, but lowering the G of B-flat diminished gives F-sharp 7, and F7 already belongs to the C diminished family). Barry credited the idea to Schoenberg.

Jazz theory, part 3: four dominants from one diminished8:36Student performances and coaching33:2934:02A word to guitar players1:08

Barry called these four dominants brothers and sisters, one family, and asked who you play with first: your brother and your sister. So the four dominants of a diminished chord are the first ones to use together. He said the average horn or guitar player thinks only in half steps and whole steps without knowing that four dominants come from every diminished chord, and that you really should know what the diminished is. He also called the guitar the best instrument, one we should learn from.

Jazz theory, part 3: four dominants from one diminished9:10A word to guitar players0:34Believe: a talk to musicians19:41Jazz theory, part 3, with score9:16

Barry rejected the usual definition of the diminished scale as an alternating half-step/whole-step pattern: if that’s all you know, he said, you miss most of the music, because so much of it comes from the diminished. For him the scale is the diminished chord plus the four roots of its dominants, and those four roots form a second diminished chord, so the scale is two diminished chords put together. Start on the root of one of the dominants and you get the half-step/whole-step pattern; start on a note of the diminished chord and you get whole-step/half-step.

Believe: a talk to musicians5:10Jazz theory, part 5: the sixth diminished scale3:133:50Student performances and coaching34:42

Barry had a student hold a C7 with just two notes and place major triads from its family above it: an A triad, a C triad, an E-flat triad. The chord has to sound pretty. With the E-flat triad on top, add the E natural next to the E-flat; without it the sound reads as a minor 7th rather than a dominant.

Jazz theory, part 3: four dominants from one diminished9:109:4410:15

The twelve notes divide into two whole-tone scales and into three diminished seventh chords, and nothing goes beyond those twelve. Barry reminds the class of this as a basic fact to know before working with diminished chords.

Jazz theory, part 2: drop voicings4:58

Everything is minor thirds, Barry says; it is the most important interval of all. The whole-tone scale gives you major thirds, but the diminished chord gives you minor thirds. So the major keys a minor third apart, C, E-flat, F-sharp and A, are brothers and sisters: one family. C major’s family is E-flat, F-sharp and A, and you practise them together.

Jazz theory, part 1, with score4:23

In a class in Bilbao, given through a Spanish interpreter, Barry described the diminished scale as the four notes of the diminished chord combined with the roots of the dominants it relates to. Each diminished note therefore sits between two of those roots: E-flat, for example, is surrounded by D and F. Exercise: from a diminished note, move to a neighbouring note and come back to the original, and do this through every inversion of the diminished chord.

Diminished chords0:331:091:412:18

The first way to modulate, Barry says, is with the diminished chord. He calls the diminished the ruler: you may think you are heading for G, but the diminished can say no and take you to F, B-flat or C instead. One diminished chord can lead you into several different keys.

11 March 2016, part 2: the diminished as ruler2:39