This is a portable machine meant for fun and light recording – and with 76 keys, it’s also an inexpensive way to familiarize yourself with the layout of the piano keyboard. Normally a keyboard with 76 keys would not be portable to me but this keyboard is very light. The Casio WK-225 portable keyboard gives you a mountain of features in a trim 76-key package with an super-affordable price. The keyboards feature a 5-song and 6-track recorder. In addition, Casio delivers 600 built-in tones which include stereo grand piano tones. This keyboard is for a beginner, and is a great keyboard for beginner to use because it comes with Casio’s “step up lesson system” which helps any beginner really understand how to compose music and learn basic progressions in music.
According to several user reviews, they have praised Casio WK-225 for the 600 voices + 8 of your own; Can record up to 10 songs; Built-in lessons, challenges & chord guides; Lightweight at just over 15 lbs. Also, some users have complained it for no sustain pedal included; Awkward touch-responsivity.
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To restoring Casio WK-225 to it’s factory settings, just simply power ON while simultaneously holding the [SONG BANK] and  of the 10-key pad buttons. When the display appears “Pls Wait”, release all buttons. The Factory Reset procedure is complete.
Warning! This operation returns all data and settings you’ve made in the menus to their factory-set condition. So be sure to back up any information you wish to keep. This procedure also applies to the CTK-4200 and WK-220 units. Hopefully the article of “Reset Casio WK-225 76-Key Portable Keyboard” can help you.
Reference: Casio WK-225 manual