Four dominants from every diminished chordThe dominant family

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

Play a diminished seventh chord and lower one note at a time by a half step: each time you get a dominant seventh chord. Barry credits Schoenberg with stating the rule: lower the C of C diminished (C, E-flat, F-sharp, A) to B and you have B7. He called the guitar the best instrument for really learning the diminished, and said guitar players especially are supposed to do this.

Believe: a talk to musicians20:1520:51Jazz theory, part 4: borrowing diminished notes3:20Jazz theory, part 5: the sixth diminished scale0:36

Barry learned the lower-one-note trick years ago, from other players and from listening to records where he came from, long before he found out that Schoenberg had written it down. He could not have afforded Schoenberg’s book back then.

Believe: a talk to musicians20:51

Barry asked why Schoenberg only said to lower the note. Raise it instead: raising the C of C diminished gives C-sharp, E-flat, F-sharp, A, a minor sixth chord on F-sharp. Raising any one note of a diminished chord gives a minor sixth chord, which you might also call a half-diminished.

Jazz theory, part 4: borrowing diminished notes3:206:18Jazz theory, part 5: the sixth diminished scale0:36

Now move two notes at once. Lowering or raising two neighbouring notes gives a major sixth chord: on C, E-flat, F-sharp, A, lowering C and E-flat gives B, D, F-sharp, A (D6), and raising them gives C-sharp, E, F-sharp, A (A6). Moving two notes that are not neighbours gives a seventh chord with a flat five. So one diminished chord leads to dominant sevenths, minor sixths, major sixths and seventh-flat-five chords. Then learn the progressions these make.

Jazz theory, part 5: the sixth diminished scale0:361:15Eyes of the Masters: the first progression1:201:54