There are 88 playing keys and one 'master' key with an animation curve for an down-up motion which can be copied to the other keys (the animation curve is only in the .blend file).

My goal when I made them was to have a set of keys that looked authentic for an old piano and were approximately the right dimensions over all so they would have realistic angular rotation and drop when 'pressed'. They are not technically accurate in all respects however as I had to interpolate some aspects of the normally unseen parts. The 'visible' parts are the most accurate, and they look nice once installed in a case.

The .blend file includes the basic geometry and
materials for the keys plus subdivision surfaces set to level 2.
Each key is a separate object. In the .blend I locked rotation around the y and z axis in the transform properties to make 'pressing' the keys easier. To move one, go to Object Mode, right-click on a key and press the R key twice. Then drag your mouse. There is no limit on degree of rotation. (This feature requires Blender 2.41 or above.)

The .obj and .lwo exports includes only the basic geometry for the separate objects and their materials. Subdivision surfaces will have to be applied by you in your program. Use a low setting.