Time to time I come across old uprights with a birdcage action. Their name comes from the arrangement where the dampers are located over the hammers, and they are connected to the whippens by long wires. When you open up a piano like that, it does somewhat look like a cage.
These pianos are notoriously difficult to tune. Firstly, because they are very old. Manufacturers largely stopped building pianos like that by the 1930’s. On many examples the iron plate does not cover the pinblock, and the tuning pins are just too lose to hold the tuning properly.
Also, these pianos pose a challenge to tuners, as we cannot use our felt mute strips, as the birdcage action usually allows no access to the strings. Some technicians remove the entire action, put in the felt strip, put the action back, tune the middle strings, action out, strip out, action back, etc. Or, we tune without the felt strip using our rubber mutes as we go along. But this latter technique is cumbersome enough as it is tricky to place the rubber mutes, or Papp’s mutes in between the wires holding the dampers. A torch is usually used in order to find the right string behind the complicated action mechanism.
While I do tune birdcages, I have had to abandon tuning a number of them, simply because they did not hold the tuning. The shame is that most of these pianos have a beautiful case, often with candle holders, and they make a nice peace of furniture. So, they are difficult to say goodbye to.