Mass storage device not included Just Plug your favourite USB Stick with your MP3's, And Jam with the UA-10.DJ-Tech is proud to announce the first worldwideGuitar amplifier with MP3 Player built-in.Get acess to LOOPS , DSP , Fast Search, or connect And optional pedal to star tthe MP3 Player.You will never be alone again on stage , or at home. Pluck and Rock your USB Player!!!