Here’s an intriguing detail about the bass line in this mix: it’s basically mono throughout most of the song, but suddenly widens out into stereo just for the first iteration of each triple-chorus (ie. 0:00-0:08, 0:45-0:55, and 1:40-149). So why might the producers have done this? Well, there are two main reasons I can think of. Firstly, stereo widening inherently has the subtle psychological effect of bringing the widened sound closer to the listener, and that seems in keeping with the greater musical importance of the bass riff at those moments – it’s pretty much the second most important feature after the vocal hook. Of course, they could have have highlighted that bass part just by riding up its fader, but the advantage of using an increase of stereo width instead is that it eats up less overall level headroom and therefore incurs less of a subjective volume penalty when played on loudness-normalised playback systems.
Secondly, I wonder whether the mix as a whole would have felt undesirably narrow without the bass widening at 0:45 and 1:40, given that both of those sections lose both the production’s main stereo track (the drums) and the assertively stereo-widened lead rap vocal too. Those sections certainly do seem to lose some ‘air’ and slickness if you mono-sum them – although, to be fair, it’s tricky to know whether it’s just the loss of the bass widening that causes this, or also the narrowing of the stereo delay effects on the vocal hook.