So if an A is 440hz, why does a piano playing an A sound different than a violin, a guitar, or someone’s voice making that same A 440 note? It’s obvious that the pitch is the same on each instrument but each instrument has a distinct sound. I’ve never heard an A on a piano and thought, is that a piano or a cello. Why can we distinguish between instruments?
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I highly recommend this Netflix kids show called StoryBots just in general. I legit learn new things while my Little Human watches it. For your question, there’s an episode about [How Music is Made](https://youtu.be/WRvX67aPHZo) .
🎶melody, harmony, rhythm, timbre, and intensity! 🎵
A cello string vibrating at 440hz is also vibrating at a bunch of other frequencies like 220 and 110 just to start, nice even multiples or fractions of 440. and thousands of others as well. The shape of the instrument amplifies some frequencies and mutes other so you get in the end an unique “signature” made of the combination of all these waves. Even two cellos would have slightly different sounds an expert might be able to tell apart. A piano has a different sized string, different shapes, and of course is not played with a bow, so it will have a very different signature. If you took a cello string and a piano string and just stretched them across a couple of nails on a 2×4, they would sound much more alike.
Another good example of the weirdness of timbre is when you breathe helium. Your voice sounds high pitched and squeaky. But if you sang a 400Hz note after breathing helium, it’s still going to be mostly 400Hz. But just like a cello, your vocal chords are also vibrating at 800Hz and 1600Hz etc. The helium does not alter the frequency of your voice. It alters which frequencies are amplified. so you are still singing 400hz but the 800 and 1600 hz tones are amplified more. That’s a different Eli5 but for simplicty think of helium as changing the instrument and not the note.
The occurrence of single, pure tones are rare in nature. Most sounds we hear are actually composed of the product of many sounds occurring together, at once, which can be likened to a chorus of sounds, not just a single voice. Usually the sound of this chorus is a jumble of randomly pitched voices, which we call ‘noise.’ Our senses are primevally conditioned to regard these with disdain or alarm. However, in some special occasions—like when musical instruments are generating them—the chorus consists of a numerically-ordered hierarchy of pitched voices, creating what is called a ‘harmonic series’, which we are primevally conditioned to desire and to derive pleasure from. These special sounds—*ordered* sounds, we call ‘musical’ because they please our senses. It’s how our brain works: we derive pleasure from musical sounds and are alarmed or discomforted by noise.
What the sounds made by different instruments all have in common is only the first, or loudest voice, called the ‘fundamental’ voice which *predominates*—and thus determines the pitch that we hear. That ‘voice’ is the same on all instruments. However what distinguishes the sounds from different instruments—what produces their distinctive sound character, is the effect of all the rest of the accompanying chorus of ‘voices’ –their distinctive loudnesses in the mix, and their distinctive decay rates, or how quickly they attenuate or persist within the sound.
Among tone/timbre and tone/timbre envelope which others said, there is another reason instruments sounds the way they do and I would say it is as important as the overtones and the frequencies involved.
That’s the volume envelope. That’s how the volume changes in time, a guitar or a piano will have a fast attack and fast release. While a gong will have a very slooooooow release as once hit it will continue sounding for more than a second. A cello will have a slow attack due the arch needs time to resonate with the string so its like a fade in, while the piano has a hammer that hits so it’s like a big volume for just milliseconds.
In electronics synthesizers envelope plays a role as important as the tone. For example you can model from a flute to a tubular bell or a music-box using the same tone (sine wave) but using different envelopes. The flute has small variations of volume due to breath or vibrato but it’s mostly constant, the tubular bell starts instantly but the volume fade away sloooowly, and the musix box is like an instant hit, it start and ends in a fraction of second.
No instrument plays a pure sine wave tone. The note you hear is the fundamental, e.g. 440 Hz, but there can be dozens of over/undertones mixed in. This is the timbre others have mentioned, exactly what an instrument sounds like that distinguishes it from all others. Look up polyphonic or overtone singing by Anna Maria Hefele on YT for a great intro and demo on overtones.
Those additional frequencies will interact with each other either constructively or destructively, depending on their strength and the instrument played, creating additional harmonics and beats that wouldn’t normally be there when the instruments are played alone.
I heard trumpets that sounded similar to electric guitars at a Voo Doo Glow Skulls concert before.
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