BMW has a solution for that and it's called ASD.
Here you can hear melodic sound of a straight six in your 4 cylinder BMW but only while you're inside. Outside it sounds like a diesel clattering from all the direct injectors.
I wonder what the 2.0L 3 cylinder turbo from a 600HP Koenigsegg Gemera sounds like?
The sound is so distinct and is only heard by select billionaires or some lucky journalists!