The Gbm/Db chord is a Gb minor chord, with the Db (the 5th) as the bass note.
The Gb minor chord itself has a dark, melancholy sound. Playing the 5th of the chord (in the case of Gbm, the 5th is Bb) as the bass note, can make the chord sound even more dark and dramatic, even if it is only a subtle difference.
The chord is also referred to as G flat minor over Db, or Gbm ‘slash’ Db, or simply, G flat minor with a D flat in the bass.
Technically, the G flat minor chord with the D flat in the bass is a second inversion G flat minor chord.
Some Gbm/Db Chord Theory and Info
- The Gbm/Db chord contains the notes Db, Gb and A (B double flat).
- It is a Gb minor chord with a Db in the bass.
- The root note of Gbm/Db is Gb, the bass note is Db.