Corpus studies of harmony in popular music normally assume a singular tonic pitch assigned to scale-degree 1, which highlights similarities in chord organization between parallel keys. Recently, Nobile (2020) posits a “double-tonic complex” in rock, where two tonics—a major chord and its relative minor—are active simultaneously, such that similarities in chord organization manifest between relative keys. Using Kullback-Leibler divergence as a metric, I assess in a corpus of classical music and a corpus of popular music how well chord organization given a minor tonic is modeled by chord organization in the parallel and relative major. I show that chord organization in the classical corpus is modeled well by the parallel key encoding, but chord organization in the popular music corpus shows mixed results. I thus suggest that corpus studies of harmony in popular music should account for the two different ways (parallel and relative) that chord organization given a minor tonic corresponds to a major key. Possible strategies include separate analyses, dual encodings, and six-based minor.