Beyoncé has designed an album that reflects a dual personality. The first side (I Am…) demonstrates her vulnerability, while the second half exudes attitude and assertiveness. From the first set, “If I Were a Boy” and “Disappear” are acoustic downtempo tunes. On the opposite end, her larger-than-life voice is perfectly suited to the sonic enormity and melodrama of “Halo.” She is one of the few performers who can swiftly shift from a song like “Ave Maria” to the booty-shaking uproar of “Single Ladies (Put A Ring On It).” And her sass and swagger matches the fearsome throb of “Diva.”