Deep down, Joni Mitchell has always been a jazz singer. Though her compositions center on life lessons and other writerly observations, what animates them are the intricate melodies — jackknifing, sharp-cornered lines that demand to-the-syllable specificity. On Both Sides Now, Mitchell applies that precision to tunes that have been famously blubbered over for decades (plus two of her own songs). Where Linda Ronstadt and other pop singers who have covered jazz standards tend to lean on oversize crooning (most recently and abhorrently, George Michael), Mitchell knows that the romance vanishes when the lines are exaggerated. So she concentrates on the melodic essence of torchy warhorses like “You’ve Changed” and “Stormy Weather,” boiling away the frills until all that’s left are haunting, painfully stark declarations. Singing atop a velvety orchestra, sounding buoyant one minute and betrayed the next, Mitchell interprets “At Last” with slurry, smeared-paint gestures and gives “Don’t Go to Strangers” a weary, Billie Holiday-worthy soul ache. It is Mitchell’s emotional generosity, not the fabulous surroundings, that winds up mattering most: After years of spinning yarns heavily dependent on words, she’s telling these stories with a repertoire of gingerly placed inflections and anguished sighs, tools she’s always had but never flaunted.