A country album in the No. 1 slot, followed by an adult-alt singer-songwriter with the soul of an opera queen, a club diva who sidetracks her debut in all kinds of non-clubby directions, and a retro-tinged neo-soul songstress. This is the state of pop today. Or at least the state of pop's top albums this spring. But lest we think pop has spurned the disco ball or something, the other half of this roundup has four albums firmly planted on the dancefloor: Madonna, The Wanted, Nicki Minaj and Adam Lambert are all very interested in getting you to shake it. So get started by digging into the wild, wonderful world that is pop in the spring of 2012.