Here's what makes it unique:
* 12-bar harmonic progression: The 12-bar blues uses a specific, repeating sequence of chords. While there are variations, the most common form is:
I - IV - I - V - IV - I - I - IV - I - V - IV - I
(Where I, IV, and V represent the root, subdominant, and dominant chords of the key.)
* Poetic structure: While not always strictly adhered to, the 12-bar blues often follows a poetic structure with a consistent number of lines per bar, and often uses rhyming patterns.
* Improvisation: While the harmonic progression is fixed, the melody and lyrics are often improvised.
Key Characteristics:
* Strong sense of call and response: The structure lends itself to vocal improvisation, with a singer often taking a "call" followed by a "response" from instruments.
* Emphasis on the blue notes: The blues scale is often used, which features flatted thirds and sevenths, giving the music a characteristic "blue" sound.
* Syncopated rhythms: Blues often features rhythms that are off-beat, creating a distinctive groove.
Examples of 12-bar blues:
* "Crossroads" by Robert Johnson
* "Hound Dog" by Elvis Presley
* "Sweet Home Chicago" by Robert Johnson
* "The Thrill is Gone" by B.B. King
Let me know if you'd like to learn more about the history, variations, or specific characteristics of the 12-bar blues!