Yamaha PSRE-343 61-Key Portable Keyboard The Aux Line Input allows you to connect any music device with a headphone output, such as an MP3 player, a computer, a mixer or even another keyboard, and hear it through the internal speakers. Touch-sensitive keys add dynamics to your playing. Play lightly and the sound is soft. Hit the key hard and it's loud. Melody Suppressor isolates the melody of audio songs connected to the Aux Line Input jack and reduces the volume allowing you to sing along or play the lead. Battery power allows the ultimate in portability, with no need for an adapter or power outlet. (Power adapter not included.) USB to HOST port allows you to connect and interact with a wide variety of educational, music creation or music entertainment applications on a computer or mobile device.