Most Americans discovered Amy Winehouse through the song “Rehab,” a defiant yet witty middle finger to those who suggested the British singer/songwriter needed to address her substance abuse. It felt like a classic one-off novelty hit — that is, until you heard the rest of her second album “Back to Black” in full. In making the 2006 record, Winehouse drew on her childhood love of jazz and her then-recent discovery of old-school girl groups to explore her fiery relationship with her ex-boyfriend (and future husband) Blake Fielder-Civil.