A mechanism for supporting the weight of a piano lid is disclosed. One or more pneumatic cylinders and arms are used to assist a user in opening and closing the piano lid. In one embodiment, a guiding cup can be removably attached to the frame of the piano below each pneumatic cylinder. When the piano lid is open, the piston arm of the pneumatic cylinder engages the guiding cup. Because the pneumatic cylinder is not attached to the piano frame, the piano lid can be completely removed without the use of tools. Another embodiment provides a mounting bracket that fits over the rear frame of a piano, allowing the mechanism to be retrofit to any existing piano without any damage thereto.