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In a “tone-scramble” task, a listener is presented on each trial with a random sequence of tones and strives to classify it based on the notes it contains. Dean & Chubb (2017) tested listeners in five tone-scramble tasks. In each, G was established as the stimulus tonic, and the listener strove to judge which of two possible target notes were also present. Their results suggested that a single cognitive resource, “scale-sensitivity,” controls performance on all five tasks. Strikingly, scale-sensitivity was found to facilitate three of the five tasks (the 2-, 3- and 6-tasks, described below) with equal strength: a given listener was likely to perform equally well on three. The current study exploits this finding to investigate the following question: Is scale-sensitivity conferred by a single neural mechanism that is differentially sensitive to notes of different scale degrees relative to the stimulus tonic? Listeners were tested in 7 tasks. All stimuli contained 32, 65ms tones, including 8 each of the notes G5, D6, and G6 as well as 8 target notes: In the 2-task (3-task; 6-task) the target notes were all A♭ or all A (B♭ or all B; E♭ or all E). There were also four “hybrid” tasks: In the 2u3-task [2x3-task], the target notes comprised 4 each of (i) A♭ and B♭ or (ii) A and B [(i) A♭ and B or (ii) A and B♭]. Corresponding 3u6- and 3x6-tasks were also tested. The single-mechanism model predicts that one of the 2u3-task or the 2x3-task should yield performance equal to the 2- and 3-tasks, and the other should be much worse. Results confirm this pattern: performance in the 2x3- and 3x6-tasks is much worse than in the 2u3- and 3u6-tasks. This result suggests that a single neural mechanism predominates in controlling performance in all seven tasks.