Hybrid chords have 2 layers: a bass note and an upper chord layer that is separated from the bass note by at least a third. The bass note is not repeated anywhere in the upper layer. These chords are referred to by some players as shash chords since they are made up of a triad or a seventh chord, a slash symbol, and a bass note.

These types of chord structures are also sometimes referred to as hybrid voicings, since they are closely related to traditional chord structures. They are deliberately structured to create an ambiguous sound. Ambiguous textures became popular in orchestral composition in the early part of the twentieth century and are related in a broad way to the artistic movement, impressionism.

Like impressionist artists that shum ultra-realistic visual representation, hybrid voicings, which by definition contain neither a major or minor third above the bass note, give an "impression" of a chord sound. The sound is open to personal interpretation by the listener. The special flavor of these voicings may be used to harmonize specific notes in a melody or to harmonize entire phrases.

Typically, in hybrid voicings, the upper chord layer is found:

1. up a major second from the bass note 2. down a major second from the bass note 3. up a perfect fifth from the bass note

Less common hybrid voicings may also be found:

4. up a tritone from the bass note 5. up a minor second from the bass note

To construct hybrid voicings of traditional chord structures:

1. Keep the root of the original chord. 2. Choose an upper structure layer that forms a major or minor triad or forms a [Major_seventh_chord|major seventh], a minor seventh or a dominant seventh. Avoid augmented, diminished, or minor 7(flat 5) structures in the upper layer of hybrid chords since they tend to sound like more traditional chord voicings when combined with the bass note.

References

"Reharmonization Techniques" by Randy Felts, Berklee Press, Boston, 2002, pages 146-147