The full size, 88-note Yamaha Graded Hammer Standard (GHS) keyboard features a weighted action with heavier touch in the low end and lighter touch in the high end, just like the hammers inside an acoustic piano. The Pure CF Sound Engine is the result of years of piano-making history combined with state-of-the-art sampling technology and piano expertise. The sound of the renowned Yamaha CFIIIS 9' concert grand piano is faithfully reproduced, making for incredible dynamics and expressiveness. You can connect a microphone to the DGX-660 to either sing along with your playing or with pre-recorded karaoke song files from Yamaha Musicsoft. This enables the player to hear their own sound with everything mixed perfectly together from the built-in speakers. It has a wide selection of built-in styles to play along to, as well as 6 track recording capabilities, USB and Auxiliary inputs, meaning you can play along with all your favourite artists.