blues

noun

• 1 (often the blues) [treated as singular or plural] melancholic music of black American folk origin, typically in a twelve-bar sequence. It developed in the rural southern US towards the end of the 19th century, finding a wider audience in the 1940s, as blacks migrated to the cities. This urban blues gave rise to rhythm and blues and rock and roll: blues has always had a strong following in Australia [as modifier]:a blues singer
• [treated as singular] a piece of blues music:a blues in C

• 2 (the blues) informal feelings of melancholy, sadness, or depression:she’s got the blues