For Pianos, Size Really DOES Matter

When you go to a concert hall for a piano recital, there's a reason why the piano on the stage is somewhere around 8 or 9 feet long, front to back. And going down to the other end of the piano spectrum, the drop-action spinets of the twentieth century are generally the smallest standard pianos that most people are familiar with. What's the difference between these two extremes? And how about all of the pianos in between?

The larger the piano, the larger the soundboard, and large soundboards create more volume because they have more surface area to vibrate and create more powerful sound waves. But there's another even more important difference between a large and a small piano: the length (and thickness) of the piano's strings.

Yamaha Concert Grand Piano

When you think about it, the tiny spinet and the 9-foot concert grand each have to produce the same 88 pitches - from the A more than three octaves below middle C, to the highest C, four octaves above middle C. The 9-foot concert grand's lowest note employs a string that is in the neighborhood of 8 feet in length, while the spinet's lowest note has a string that is around 3 feet long on a good day. Yet both of those strings need to produce the same pitch. How is that possible?

You'll notice that on all pianos, the strings in the bass are wound with copper. The reason for the copper winding is to give those strings more mass, and thus, to create a lower pitch. If piano bass strings weren't wound with copper, they would need to be much, much longer to get the same pitches. If you observe bass strings on a piano, you'll see that the copper winding is thickest on the lowest strings, and that the copper thickness gradually gets thinner and thinner as you get into the high bass. And then, of course, you transition to the plain steel strings.

Drop-Action Spinet Piano

If you take a close look at the lowest bass strings on a huge concert grand, you'll see that the copper winding is relatively thin, compared to the same lowest strings on smaller pianos. And if you take a look at the lowest strings on the tiny spinet, you'll see that the lowest strings are so fat, they sort of resemble hot dogs.

Piano strings vibrate in very complex patterns. Without getting too far into the weeds, it's fair to say that the thinner the piano string, the better the tone will be. Very thick piano strings just don't vibrate all that well. And that's the main reason why spinets don't produce very pleasing tones, especially in the bass.

Piano strings, just like all sound-producing things in nature, produce overtones. In other words, when you play the lowest C on a piano, you're actually hearing that lowest C pitch, but you're also hearing the C one octave above, and the C two octaves above, and the C three octaves above, and on and on. And not only that - you're also hearing the G an octave and a fifth above that lowest C, and you're hearing some fourths higher up, and some thirds ... and on and on!

Suffice it to say that the thinner the piano string, the better all those overtones will sound. And the thicker the string, the more out of tune those overtones are going to be, because of the way that those thicker piano strings vibrate. And that's why tuning a spinet piano is quite a bit more difficult than tuning a 9-foot concert grand - all those overtones in the spinet are very much sharp in pitch compared to where we'd like them to be. And those sharp overtones interfere with the other notes on the piano that we're tuning. For these reasons, tuning a piano is always about engaging in compromises - trying to fit on those sharp overtones so that they sound as good (or as least bad) as possible in connection with all of the other notes on the piano. The piano's tendency to have sharp overtones is called inharmonicity.

All pianos have inharmonicity. But the 9-foot concert grand at the concert hall has very low inharmonicity. In other words, the overtones that the piano's strings produce are sharp, but they're only a little bit sharp. The tiny spinet, on the other hand, has wildly high inharmonicity, which means that the spinet's overtones, especially in the bass strings, are very sharp. Inharmonicity, then, is the most important reason why size really does matter in pianos.

In general, pianos larger than spinets but smaller than 9-foot concert grands - in other words, most pianos - have inharmonicity levels somewhere in between those two extremes. When you're considering a piano, one very important factor to consider is size. In general, whether it's a grand piano or a vertical piano, the bigger the piano, the better the tone.