Pianos typically have 88 keys, divided among 52 white and 36 black keys. Given that information, it might make sense that pianos have 88 strings. However, pianos have more than that.
Pianos range from having about 220 strings to 240, with an average falling right around 230.
The modern 88-key piano gives the musician seven full octaves plus another third, ranging from A0 to C8. However, some pianos have fewer keys, and others have more.
For example, there are large grand pianos that have somewhere between 97 and 108 keys that add notes in the lower registers. Some harpsicords have as few strings as forty.
Smaller electric keyboards have a range of 61-76 keys, giving them anywhere from five full octaves to six octaves plus that extra third. However, they do not have strings as their sounds are produced digitally.
For the purposes of this article, we will be acoustic pianos and their string composition.
Why Have Multiple Strings?
This comes down to both the musical aspect and the physical aspect. It might make sense for a lower note to have more strings to make a lower sound. Or for every note to have two strings attached for a fuller sound. But this isn’t quite the case.
The lowest bass notes will only have one string per note, but as you go up the scale into the higher bass notes and tenor notes, there will be two strings per note. The higher tenor and treble notes will have three. Where the cutoff is depends on the model.
Some manufacturers will only have one octave of single-stringed notes and then switch to two. Others won’t switch to two strings per note until two octaves from the bottom. Similarly, some manufacturers will only do one octave of two-string notes before switching up to three, others will do an octave and a half or two octaves before switching.
There is a German manufacturer that will actually have a fourth string per note at the very highest of treble notes. That string is not even struck by the hammer, it is there only to resonate with the nearby strings.
Having multiple strings for a note certainly increases the fullness and quality of sound. It is necessary to do this for the higher notes on the register because otherwise, they would be too quiet. The higher notes get more strings per note to regulate the volume on the piano, so that way, the lower notes are not automatically louder than the higher ones.
Additionally, from the physical aspect, the shorter strings are at a higher risk of breaking. Therefore, by distributing the hammer strike across multiple strings, the wear and tear on an individual small string is lessened.
Why the Variation?
When you consider that an average 88-key piano has seven octaves plus the minor third, it can be a challenge to think about where to switch up the amount of strings in addition to the string composition. Nothing divides equally.
It ultimately comes back to preference. Tonality, volume, and resonation all play a part. Manufacturers determine what works best for the pianos they make and they stick with it.
Averaging out across all manufacturers, the lowest ten pitches, which is actually less than a singular octave, will have one copper wound string. When counting chromatically, an octave on a piano is twelve keys, though only seven are played in a major or minor scale. The other five notes are the unused half steps.
The next eighteen pitches, or one octave plus a third, will have two copper wound strings. This accounts for the bottom two octaves plus the minor third.
Then the upper sixty pitches, which is the remaining five octaves, are three steel or bare wire strings.
Though, if you were running the math in your head, that is actually only 226 strings. Interesting, isn’t it?
Quality of Sound
You gain fullness for the note when the hammer strikes the two or three different strings because the hammer will not hit each string equally. Therefore, they will reverberate differently and add quality to the note.
For notes that have three strings, the middle string is usually tuned exactly to that note, while the ones on either side will be tuned anywhere from half a cent to a cent and a half lower and higher respectively. This ensures the optimal string reverberation for the best quality.
Because the strings are shorter, their vibrations will stop faster than a longer string. Thus, adding multiple strings per note, especially if they are tuned slightly off from each other, will enable similar tonal quality to that of the longer strings and lower notes.
Piano tuners must be able to tune not only every note but also every variation of the note for the notes with multiple strings. It makes more sense why they are so expensive.
Thus, it all comes down to the combination of volume and tonal quality as well as the physical limitations of short strings. You ideally want the piano to have similar volume and tonal quality from the lower registers to the upper registers. Additionally, you do not want strings breaking, hence the distribution of the hammer strike across smaller strings.
String Composition
This is very noticeable on a grand piano and impossible to tell on an upright, but the higher pitches of notes have shorter strings while the bass notes have longer ones. When tension is put on a long string, it produces a low note, versus tension being put on a short string produces a high note. This is why grand and baby grand pianos have those curved shapes.
The higher pitches will also have thinner strings compared to their lower counterparts. The bass notes also have strings wound with copper wire instead of bare steel wire. This ensures that they will be stronger.
The copper wire also enables the strings to get more reverberations on their own, allowing for the full tonal quality with a singular string versus two or three strings.
After about three octaves, the piano switches from the copper wound strings to the steel wire strings. But this can vary from manufacturer to manufacturer as much as how many strings are wound per note.
Conclusion
The average piano has roughly 230 strings, which serves as both a musical and a physical limitation function. The extra strings for the upper registers regulate volume and tonal quality. They also help reduce the stress the hammer puts on them upon striking.
You neglected to mention the pianos made by Steven Paulello and Stuart & Sons. Both have made instruments with more than eighty-eight keys; the latter recently completed a piano with 108 keys from CCC (32′ C) to b””’.