Many player pianos operate pneumatically, using bellows in order to drive the mechanism that presses down the keys. However, at times these bellows may fail, and large-scale repairs are required. Replacing the rubberized cloth of a bellows is a delicate process, but it will spare you the expensive services of player piano technicians.
Open the bottom of the piano. A metal clip should hold the base of the instrument in place; once you have unfastened the clip, remove the base. At this time you should check the bellows for damage. If the corners of the bellows are cracked, patch them with yellow rubber cement, then cover the area with cotton cloth and paint it. Repeat this process for the bellows in the top section of the piano. If these bellows are simply cracked at the corners, the patching procedure will allow you to avoid completely replacing the bellows-cloth.
Remove any excess glue from where the bellows meet the other parts of the piano's mechanism. Dampen a rag with rubbing alcohol and rub gently against any spots of glue that you wish to remove.
Remove the tacks connecting the old rubberized cloth to the wooden portions of the bellows. Use pliers or a flat-head screwdriver to gentle pry the tacks out, being careful not to damage the wood. This should allow you to remove the rubberized cloth: if it does not come off the wood, rub down the connecting sections with rubbing alcohol again. Fill the tack holes with wood putty.
Measure the section of cloth that you removed, then cut the new section of rubberized cloth to the same dimensions. Be sure not to crease the cloth while you are cutting it.
Line the edges of the wood portions of the bellows with glue, then do the same at the edges of the rubberized cloth, leaving an extra inch or two of cloth that lies flat against the wood. Press the cloth to the wood, and clamp it in place. Attach the cloth to the wood by tapping carpet tacks into the flat sections of cloth. Allow two hours for the glue to dry before you remove the clamps.
Check the vacuum seal of the bellows. Put the mechanism of the player piano into action. If the piano does not play, check to see if the bellows are compressing. If not, look around the edges of the cloth and seal holes you find with glue.
Do not completely shut the bellows at any time. Doing so creases the material of the bellows and severely shortens its lifespan. Let the bellows hang naturally.