Casio's CTK-4400 Portable Keyboard is a powerful and expressive instrument with features like their popular Step-up Lesson System that makes it easy to hear your progress as you sharpen your playing skills, plus a 5 song, 6 track recorder, audio inputs for an MP3 player and a class compliant USB port for MIDI connectivity.
The CTK-4400 also comes complete with an included power supply, but if you'd like to take your music with you, it can run on batteries. All this makes CTK-4400 more powerful and expressive than anything like it.