Classically, attentional selectivity has been conceptualized as a passive by-product of capacity-limits on stimulus-processing. Here, we examine the role of more active cognitive control processes in attentional selectivity, focusing on how distraction from task-irrelevant sound is modulated by levels of task-engagement in a visually-presented short-term memory task. Task-engagement was varied by manipulating the load involved in the encoding of the (visually-presented) to-be-remembered items. Using a list of Navon letters (where a large letter is composed of smaller, different-identity, letters), participants were oriented to attend and serially recall the list of large letters (low encoding-load) or to attend and serially recall the list of small letters (high encoding-load). Attentional capture by a single deviant noise burst within a task-irrelevant tone sequence (the deviation effect) was eliminated under high encoding-load (Experiment 1). However, distraction from a continuously changing sequence of tones (the changing-state effect) was immune to the influence of load (Experiment 2). This dissociation in the amenability of the deviation effect and the changing-state effect to cognitive control supports a duplex- over a unitary-mechanism account of auditory distraction in which the deviation effect is due to attentional capture while the changing-state effect reflects direct interference between the processing of the sound and processes involved in the focal task. That the changing-state effect survives high encoding-load also goes against an alternative explanation of the attenuation of the deviation effect under high load in terms of the depletion of a limited perceptual resource that would result in diminished auditory processing.