This will be just a short post; but two evenings ago I learned about Zelda's ghosts.
It's a good thing. I'm all jazzed up about it.
I've always wondered how tuners could hear how to tune the growly, rumbling bass strings. You can definitely hear when they are out of tune; but there's so much going on and so many overtones that -- at least for me -- it's hard to hear what exactly it is that you're tuning. That's where ghost tones come in.
Turns out that each bass string has a number of ghost tones -- more correctly, partials. When you strike a bass note you're hearing not only the fundamental note; but a series of partials embedded in the same string -- up to ten (ghost tones) partials to be exact; but primarily the next two octaves up (2nd & 4th partials) and a twelfth (3rd partial).
By holding the bass note down silently and striking the 2nd, 3rd & 4th partials independently, they will sound in the the unstruck bass string -- and, by isolating the partials you can hear whether or not the bass note is in tune. In essence, tune the partials correctly and you've tuned the fundamental sound.
I suppose that's old hat to those who've been tuning for a long time; but I was so excited about learning this that I went on a bass tuning rampage with Zelda. It's amazing. There are now crystal clear tones throughout the bass. Octaves sound perfectly together and the piano has a new depth. The rumble is gone.
That's the good news. The bad news is once the indeterminate growling vanished, it became clear there are a few notes that are of poor quality and out of character with the rest of piano. Most of the bass is rich and sonorous now. But some pop out as having a different "buzzing" quality without the depth. I suppose, in some ways, that's good news as well since I can now differentiate which notes need further attention.
On to the next step -- more reading and learning to discover possible causes -- and then make the necessary adjustments as I'm able.
But for now, I'm just happy to know about Zelda's ghosts.