Acoustics of a Piano

Here’s something you can use to amaze your friends. I’m sure you have noticed that there’s just something different in the sound of a grand piano and even the best of electronic keyboards.

It’s a physical acoustics issue. Try this on a grand piano for best results, but it will also work on studio and spinet pianos that are reasonably in tune.

1. Press down and hold the C two octaves below middle C. Don’t make the note sound. Just press the key and hold it.
2. Firmly play the C an octave above the low C, then the G above that, followed by middle C, E, G, A, B-flat, and C. Play those notes firmly and release them. Do it fairly quickly.
3. You will hear those pitches emanating from the low C that you are still holding down.

These are called sympathetic vibrations.

Here’s another demonstration you can conduct using the same principle.

1. Press middle C, E and G and hold them down without striking the string. This lifts the damper and allows the string to be free.
2. Firmly play and release the low C again two octaves below middle C.
3. You will hear a faint C triad emanating from the C, E and G you are holding down.

Now consider the fact that this is happening with every note you play when the damper pedal is pressed. That’s where you find the rich timbre of a piano. As a matter of fact, one of the reasons pianos have those very low and very high notes we don’t often play is to provide strings that will sympathetically produce those bonus notes.

The Bösendorfer Imperial Grand 290 even has nine extra low notes. https://www.pianistmagazine.com/news/general/why-the-extra-keys-the-bosendorfer-imperial-grand-piano

While these can be played, the main purpose is to allow more richness of tone with the sympathetic vibrations they provide. Check out the link. There is an interesting history of how that piano came to be. By the way this piano is a 9’6” and retails for $250,000!

If you try these experiments on an electronic piano you will find they do not produce any sympathetic sounds. You just get the note that is played. No added richness to the timbre.

It’s all part of God’s amazing creation of physical sound that is so important to us. Now go and practice your scales!

by Stan Pethel