on short KB jobs, 1 hr, NH, Cocktail hr, etc, no mixer will be required with the KORG Pa4x as it's onboard features are more then enough to cover, Style play, SMF, Mp3, Lyrics, etc,....
but in no way can it compete with a Laptop for searching, mixing,
& for independent playing with a keyboard this is where the mixer is a crucial necessity for flexibility in a rapid fire perfromance program,....a guest mic,playing with other musicians, controlling a separate SUB out in your PA system, or DJing needs are the other uses. Mixers Rock!!