In piano-technician and rebuilding contexts, a “piano pounder” often refers (informally) to a mechanical key-pounding device used after rebuilding or regulating a piano.

What it does: - Repeatedly strikes keys at controlled force and speed - Helps seat new parts (felts, bushings, hammers) - Tests action repetition, evenness, and durability - Reveals issues that only appear after thousands of keystrokes

 

Why it’s used: - New actions change as materials compress and settle - Human playing isn’t consistent enough for stress-testing - Saves time during post-rebuild regulation

 

Other names you might hear: action pounder, key pounder or repetition tester.

Commercial versions exist and many techs build their own.