Guitar Chords in D Flat Major
Diatonic Triads
The guitar chords in D flat Major. are Db, Ebm, Fm, Gb, Ab, Bbm, Co.
We'll keep all these chords in first position (and 2nd).
The key of Db has 5 flats (Bb, Eb, Ab, Db, and Gb).
The Major Keys: C G D A E B F# Gb Db Ab Eb Bb F

Get to it :
- Fret all of the guitar chords in D flat.
- Practice the Db scale.
- Play the Chord Scale (alphabetically ascending and descending [reverse]).
- Play the progression: I-vi-ii-V7-I. And, also I-IV-V-I.
- Write your own progression,
Is the diminished chord ever used?
Yes, but if you'll notice, the tones which are in the diminished chord (the viio) are the 'upper' part of the V7. So, in this sense, the diminished chord is inside or a part of the dominant 7.
We'll also see that once we convert the diminished chord into a 7th chord (either half-diminished 'from' the Major, or fully diminished 'from' the harmonic minor), it becomes much more useful. Useful in the sense of function and in terms of fingerings.

