Understanding speech in noisy environments relies on the brain's ability to selectively attend to a target speaker, filtering out background distractions. Research suggests that musical training enhances this ability, likely due to improved auditory processing, but the underlying neural mechanisms remain unclear. Neural activity in the auditory cortex tracks the speech envelope, particularly within the delta (1–4 Hz) and theta (4–8 Hz) frequency bands, which are crucial for processing speech in noisy settings.

In this study, we examined the effects of selective attention and musical training on cortical speech tracking using magnetoencephalography (MEG) to record neural responses in 52 participants, both musicians and non-musicians. Participants focused on one of two competing speech streams, allowing us to measure how attention and musicianship influence neural tracking in the delta and theta bands.

Our analysis revealed that selective attention significantly modulates delta-band tracking, enhancing neural responses to the attended speech stream. Theta-band tracking, however, did not show significant modulation by attention, suggesting its primary role in lower-level acoustic processing, such as syllable parsing, regardless of focus. This aligns with findings that delta-band activity supports higher-level linguistic processing.

Interestingly, musical training did not significantly affect speech tracking in either the delta or theta bands. Both musicians and non-musicians exhibited similar neural responses, challenging assumptions that musicianship enhances all aspects of auditory processing. These findings suggest that while musicians benefit from enhanced auditory fitness, these advantages do not significantly affect cortical speech tracking. This is consistent with studies showing musical training enhances subcortical responses, with limited effects on cortical processing.

In conclusion, our study highlights the importance of delta-band activity in selective attention during speech perception in noise, while theta-band activity plays a more consistent role across both target and distractor speech streams. Furthermore, our findings challenge the view that musical training significantly alters cortical mechanisms of speech tracking, suggesting that its effects may be more limited to other auditory processing domains. These findings suggest that musical training's effects may be more limited to other auditory processing domains.