I want to practice Beethovens moonlight sonata, but the sonata needs keys lower than what I have in my 76-keyboard. Is it possible to shift keys one octave down?
Yes, there is a function in all Yamaha keyboards in this product line where you can transpose the keyboard by any interval you need.
You should be able to download the owners manual as a PDF at this link.
The instructions say:
1) Press the Function button
2) Use the Category buttons to select the Transpose item.
3) Use the dial to set the transpose value between - 12 and + 12 as required.