DOWNLOAD THIS: Whaddaya know—Epic’s Meghan Trainor has just retaken the top spot on the iTunes singles chart from Big Machine’s Taylor Swift, whose “Shake It Off” had owned #1 since it came out in mid-August. Was “All About That Bass” aided by Trainor’s appearance on The Tonight Show With Jimmy Fallon last night? Broken Bow/RED’s Jason Aldean has crashed the pop party with a pair of instant-grat cuts off his pre-order. And how about the durability of “Chandelier” from RCA’s Sia, which just keeps hanging around with the big boys—or big girls, to be more accurate? On the albums side, Interscope’s Maroon 5 and Def Jam’s Jeezy are marching in lockstep toward their expected order of finish on next Tuesday’s chart, while Jhene Aiko gives Team Bartels two entries on the big board, same as Aldean, and a $6.99 price tag has brought RCA Nashville’s Miranda Lambert back into the picture. (8/29a)