An augmented chord is a major chord with its fifth raised by a semitone. Caug is made of C, E, and G♯, which gives a floating, tense quality that does not commit to where it will go next.
The basic idea
Because the intervals between its notes are nearly equal, the sense of direction is ambiguous and the sound is distinctive. It is used as a color when you want to make a bright major chord slightly unstable.
Its role in writing and performing
It is handy when you want the bass or an upper voice to move by semitones inside a progression. It adds a dramatic lift or a dreamlike instability and builds expectation for the next chord.
How to try it in a DAW
Raise the G of a C chord to G♯ and alternate between C and Caug. Moving on to Am or F next lets you hear how the upper note shifts by a semitone.
How it differs from related terms
A diminished chord also sounds unstable, but its notes and its direction of resolution are different. Like a tension chord, it is one option for adding color to a basic chord.
When you want a little unexpected color in a standard progression, try a short augmented chord.
