Piano Magic Tricks

These tricks will work on an acoustic piano. You need strings vibrating physically in the instrument. I don’t know if it would work on an electric piano like a Rhodes or a Wurlitzer, which are essentially electric celestes, but it shouldn’t on an electronic piano.

[I don’t know if you can identify the notes on a piano. To do these you’ll need to be able to do that, to know the note names. If you’re interested and you can’t identify notes, a picture of a keyboard with letters on the keys should be really easy to find on line. On a keyboard, “up” is to the right and “down” is to the left because we’re talking about pitch, not physical position. Same by extension with “above” and “below.” On a guitar, the lowest string is physically the highest, but we talk in terms of pitch. An octave higher means the first same letter note to the right. Each octave will be in the same position relative to the groups of two and three black notes.]

Find Middle C. If your piano has the name of the maker on it, that C should be about in the middle of that name. Go an octave down to the next C. We’ll use that note in all of these examples. This choice is arbitrary, as everything I’m about to explain is based on intervals, which is to say the distance between two notes.

Press that C’s key down gently such that you don’t hear a note. What you’re doing is taking the damper, which deadens the strings, off the strings on that note so that they can vibrate freely. Go to the G just higher than that C (still below middle C). Hit it hard and immediately release it. A note will ring. The note that rings will be the G above middle C. When you take your finger off the low C, the ringing will stop. Now reverse them: press the G down gently and strike the low C hard and immediately release it. The same G above middle C will ring until you release the G key you’re still holding down.

In all of these cases the keys are reversible like that. Hold either one down, strike the other, and the same third note will ring. The ringing always takes place on the undamped string, which is to say the string of the key you’re holding down, so you’re getting the same ringing note on two different strings when you reverse.

Go back to the low C. Now hold it down and strike the F just above it hard. The note that will ring will be the C above Middle C.

Go back to the low C. Now hit the A above it hard. This time an entirely different note will ring: the E just over an octave above Middle C.

What’s important about the notes I chose is not where they are but how far apart they are. To put this in interval language: Hold down a note, strike a perfect fifth above it, the note an octave above the perfect fifth rings. Hold down a note, strike a perfect fourth above it, and the note two octaves above the lower note will ring. Hold down a note, strike a major sixth above it, and the note two octaves and a major third above the lower note will ring. So if you moved my entire exercise up or down it would still work.

However, if you were to hold down that low C and strike, say, the F# above it, a tritone higher, if you heard anything ring at all it would be really high up. This doesn’t work on all notes equally.

Now I’m going to explain why this works. If you found my YouTube comment in the main thread of the overtone singing video on my last post, you’ll know some of it. I’ll assume you didn’t.

When a string vibrates, it doesn’t only vibrate at one pitch. It contains other pitches called overtones, harmonics, or partials. How this happens is that while the string is vibrating along its whole length, which is the nominal pitch of the note – called the fundamental in this context, it is also vibrating in halves, and each half is an octave above the original pitch. All octaves involve vibrating twice as fast (or half as fast in the other direction). That’s what an octave technically is. It’s also vibrating in thirds three times as fast, in quarters four times as fast, etc.

The overtone series works like this:
2x  as fast: an octave up
3x: an octave and a perfect fifth
4x: two octaves (doubling twice)
5x: two octaves and a major third
6x: two octaves and a fifth (3x an octave higher)
7x: two octaves and a somewhat flat minor seventh
8x: three octaves
9x: three octaves and a major second
10x: three octaves and a major third (5x an octave higher)

This doesn’t only work on strings. It works on anything mechanically producing a steady pitch.

The relative loudness of these overtones to the fundamental and to each other is one of the things that determines timbre, or what a sound sounds like. Those relative loudnesses also change with louder sounds, so when you hit a key hard the sound itself is different than if you hit the key gently, not just louder. If you listen to someone screaming on the radio or TV, you can turn them way down and still tell they’re screaming. Relative loudnesses of overtones are also what determines vowels – your mouth filters overtones by making different shapes.

The process we’re using for these tricks is sympathetic vibrations. Sympathetic vibrations are when air vibrates at the same speed that a string is tuned to, thereby vibrating that string. The louder the sound (the more extremely the air vibrates, which is to say the greater the swings in air pressure), the louder the sympathetic vibration is likely to be. What you’re hearing ringing is the lowest note which the overtone series of the two piano keys share. Because that note shows up in the overtone series of both keys, either key can trigger sympathetic vibrations on the strings of the other.