Guitar players, Horn players, Keyboards.... anyone who wanted to change tone. Miles Davis in his Fusion years. Most the Great players have a pedal of some type onstage or in the Studio. Check any live Music pics out to see what your Favorite artist is using.
Here is Just a Little on Stombox History by Art Thompson
STOMPBOX – A HISTORY OF GUITAR FUZZES, FLANGERS, PHASERS, ECHOES, & WAHS