The flagship of the new privia line, the Casio privia px850 digital piano has the advanced air sound set providing an additional level of realism including grand piano lid simulation and sympathetic resonance. The px850 has a dual 20w speaker system and a cabinet that opens providing a rich concert sound. The new privia px850 represents a significant step in the continuing evolution of the privia digital piano line. A combination of a new keyboard action and a powerful new sound engine provide a new level of detail, nuance and expression for a superior grand piano experience in the lightweight and stylish design that privia is known for. The Casio px850 has 18 instrument tones (5 are piano), and 256 note polyphony. The px850 keys feature damper resonance, hammer response and sympathetic resonance. A very special other feature is the lid simulation. You can choose (separate from what the actual px850 cabinet will do) whether you want the lid on the grand piano open, closed, half or removed. The px350 has 1/4 inch audio outputs and usb-to-device output so you can easily connect the privia px850 to recording and sound reinforcement equipment.