shorter answer: u sort of can't
longer, fl studio exclusive answer:
u could kind of rig something up in FL studio, but it might be more hassle than it's worth. to explain, a bit about stereo imaging as a concept. sound is perceived as "wide" when there is difference between the Left and Right channels. sound is perceived as "narrow" when the sound is the same in both Left and Right channels. you would need something that switches between the mono output and stereo output.
the
Fruity Stereo Shaper plugin can create Mono output from Stereo input by adding the Left and Right channels of the Input together, dividing them by 2, and then putting the sum of those channels out through both the L and R channels, so it's the exact same Mid signal coming out of both channels. within the plugin, it looks like all 4 of the sliders at 50%, for reference. im pretty sure that's how FL's other plugins create Mono outputs, just in the background.
&& there's another plugin, the
Fruity Peak Controller, that controls parameters based on an Input signal (think like Sidechaining, but u can make it affect anything you link it to). you split the L and R channels of a source to separate Peak Controllers, and have them control the Fruity Stereo Shaper's L->R, L, R, and R->L settings, so that when a source gets louder, it gets wider (or vice versa).
im fairly certain it would get the result you're looking for. idk if there's an analogue to the Peak Controller in other DAWs, though. i'll give this a shot tonight and update.
