Comment by 4k93n2

if the phone is in your pants pocket then its fairly trivial to change the volume just by using the buttons on the phone

even some of the cheapest in-line remotes that only have a single button will let you change the track by double tapping it

if you dont have an in-line remote then theres also the option of using a key remapper app (probably not on iphone) to let you change track by long pressing the volume buttons