imagine a group of friends all in the car together, jamming to music. there are too many people to comfortably fit in the car, so person a is sitting on person b’s lap in the backseat, whether they’re a couple or not. person b loves the song that’s playing, and it just so happens they know how to play said song on the guitar / piano. unfortunatey, they have no instrument, so instead they take to playing person a’s ribs / sides / stomach while they have nowhere to move due to how cramped the car is. depending on how ticklish person a is, it might go unnoticed, their giggling too quiet under the blasting music, their squirming taken as discomfort from sitting on person b’s lap. or, their laughter is so loud it can be heard over the music, drawing everyone’s amused attention.