Otis Spann was Muddy Waters' pianist for nearly two decades -- the left hand that held Chicago blues together. His piano style could shout and whisper in the same bar, rolling boogie-woogie bass lines underneath stabbing right-hand chords. Without Spann, the Muddy Waters band didn't sound like the Muddy Waters band.

He was half-brother to the pianist Muddy Waters had before him, and he stepped into the role in 1953 like he'd been born for it. When he wasn't backing Muddy, he made his own records -- Otis Spann Is the Blues with Robert Lockwood Jr. on guitar is one of the great Chicago blues albums of the 1960s.

He died of liver cancer at 40, and the Chicago blues scene lost its greatest piano voice. Muddy kept playing, but the sound was never quite the same. The left hand that held it all together was gone.

Otis Spann was Muddy Waters' pianist -- the left hand that held Chicago blues together for two decades. The greatest blues piano voice of the era. Dead at 40. Muddy's band never sounded quite the same.