Author Summary Attention is the cognitive process underlying our ability to focus on specific aspects of our environment while ignoring others. By its very definition, attention plays a key role in differentiating foreground (the object of attention) from unattended clutter, or background. We investigate the neural basis of this phenomenon by engaging listeners to attend to different components of a complex acoustic scene. We present a spectrally and dynamically rich, but highly controlled, stimulus while participants perform two complementary tasks: to attend either to a repeating target note in the midst of random interferers (“maskers”), or to the background maskers themselves. Simultaneously, the participants' neural responses are recorded using the technique of magnetoencephalography (MEG). We hold all physical parameters of the stimulus fixed across the two tasks while manipulating one free parameter: the attentional state of listeners. The experimental findings reveal that auditory attention strongly modulates the sustained neural representation of the target signals in the direction of boosting foreground perception, much like known effects of visual attention. This enhancement originates in auditory cortex, and occurs exclusively at the frequency of the target rhythm. The results show a strong interaction between the neural representation of the attended target with the behavioral task demands, the bottom-up saliency of the target, and its perceptual detectability over time.