Yamaha PSRE253 61-Key Portable Keyboard 61 full-sized keys are great for learning and developing keyboard playing technique. Duo mode splits the keyboard into two halves, each with their own "middle C" for practicing with a partner 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. The Portable Grand button and instantly resets the keyboard to the grand piano Voice 32-note polyphony allows for the performance of beginner to advanced level pieces, allowing for sustained notes to ring through without being cut off. The PSRE253 operates on batteries or with a power adapter. NOTE - Power Adapter is sold separately.