This piano tuning blog is a companion to our How to Tune a Piano Yourself tutorial. In this blog we expand on the tutorial with new information and perspectives on do-it-yourself piano tuning. If it is your first time here, visit the tutorial first.
The self-tuning piano has been a holy grail item for pianists since the pianoforte was born. Piano owners all know the heartbreak of a piano going out of tune. It's inevitable, even for the lovingly maintained piano. The process of detuning begins the moment the piano tuner lifts his wrench from the pin.
The obvious method would be some sort of motor to turn the pins. But, apparently that's not so easy. How do we know? No one has done it, at least commercially.
Don Gilmore, inventor of a self-tuning piano, has a different idea. He tunes the strings with heat. He passes an electrical current through the string. The resistance in the string causes it to heat. When the string heats, its pitch flattens. Electrical current provides the fine control needed; he claims a tuning accuracy within 1/1000th of a cent. The control circuitry is a dedicated box, able to analyze the pitch and adjust automatically. All that travels to each string is a wire to the pin, accessed from behind the soundboard. No need to squeeze in a bunch of mechanical apparatus. The basic design of the piano needs little modification.
(Incidentally, this is why you should not mute strings with your fingers. The heat from your body will change the pitch of the string! And it leaves fingerprints.)
The desired values are first determined by tuning the piano by hand. These are recorded, then used as the reference for the electrical tuning values. It's even possible to change temperaments easily, perhaps even between pieces in a performance.
The piano is intentionally tuned sharp (or, to be more precise, tuned true in an environment with a higher than average ambient temperature), so that a current must be present to be in tune. Therefore, the unit must be powered on any time the piano is played. Once switched off, the piano reverts to its detuned (sharp) state. The current required is pretty small, though. The system is capable of some significant correction, so it can continue to adjust as the base tuning degrades. It takes about a minute to prepare the piano for playing, per the video.
An observation that jumps to my mind is that the heating flattens the strings, so they must be detuned sharp for the system to have an effect. My piano reliably goes flat over time. I presume that eventually some strings will need to be pulled back to sharp so the self-tuning system can continue to work. Furthermore, the inharmonicity of the piano can change as the materials age. Piano tuners are quick to tell you that tuning to a table of values will give you a mediocre result, and I don't see this method entirely overcoming that. From time to time, I would expect that the reference tuning of each piano will need to be reevaluated for the best sound.
I think the system, which is in the prototype stage, has potential. It's relatively simple, with minimal change to the piano itself. Yeah, you have to plug in, but that may be a small price to pay for a piano that tunes on command.
I didn't know that there was such a thing as a self-tuning piano, how cool. I wonder how difficult it would be to change the tuning during a performance like you say is possible. Would you have to hire an additional technician to be able to do this? I bet a stage hand could do it, especially since it tunes itself. I will have to show my brother-in-law this, he plays piano.
88 x 3 stepper motors? I can't imagine the noise and heat that would create. This idea of heating the strings is brilliant!
Wow! Make your piano a potential death trap, to tune it, perhaps add a bright enticing light inside and with the top open it will kill flies as well?
"Pass current" through every string, well that's very inefficient, in our ever demanding eco friendly world. Ok, so its probably going to be extra low voltage, but couldn't they just design a simple geared stepper motor to rotate the pegs, at least then it would stay tuned. The electronic control system could lower the note first and then slowly bring it up to match the stored value, whenever tuning was required. Then at least you'd only have to plug it in to retune. If this is purely a retro fit issue, then the motors will just need to fit on existing tuning pegs, in a similar modular fashion as the sustaining module.