Most listeners (70%) struggle to classify randomly-ordered, major vs. minor tone sequences (Chubb et al., 2013). This study investigated whether introducing simple rhythmic and/or sequential structure to these stimuli could heighten sensitivity in such tasks. Listeners participated in 8 tasks. Stimuli were tone-scrambles, which are sequences of pure tones comprising equal numbers of a target note T plus notes G5, D6, and G6. In “3-task” (“4-task”) variants, T was either Bb or B (C or Db). On each trial in a given task, the subject heard a single stimulus and strove (with feedback) to guess T. In “fast” task-variants, each stimulus contained twenty, 65ms tones. In “random” task-variants, the tones were randomly ordered. In the “FR” (fast-random) variant, stimuli were presented in an unbroken stream. In the “FRwR” (fast-random-with-rests) variant, a 130ms rest was inserted after each successive block of 4 tones. In the “FCwR” (fast-cyclic-with-rests) variant, the first four tones included one each of G5, D6, G6 and T, and this sequence repeated 5 times, each time isolated by rests. In the “Slow” variant, each stimulus comprised 1 each of the notes G5, D6, G6 and T played at 325ms/tone in random order. Results and Conclusions: In the 4-task, performance was ordered from best to worst as follows: FRwR > FR > FCwR > Slow, and all differences were significant. The 3-task variants followed the same pattern, but the difference was significant for only the Slow variant. Post-hoc analysis revealed that the suppressed performance in both the Slow and FCwR task-variants is due to a powerful bias inclining listeners to respond “major” (“minor”) if the 4-note sequence defining the stimulus ends on a high (low) note. Importantly, the current results indicate that inserting regular rests into random stimuli can heighten sensitivity to the target note difference.