I will start off by saying that you dont need to know any of this.
Now that I get that out of the way, I will say that this whole subject can be endlessly fascinating. If you like music and you like science, you will not be sorry you read this. The science behind sound is incredibly fascinating, the science behind music even more so.
Chances are, if you have done any sort of higher science (by which I mean high school or above), you have heard of hertz. The term is used to describe not only sound, but light and several other things as well. It can most easily be described as cycles per second, or, in other words, how many times an event takes place per second.
In sound, this event is vibrations. As an example. The A above middle C is at 440 Hz (abbreviation for Hertz). This means that whatever happens to be producing the sound is vibrating 440 times per second (approximately, were not perfect tuners). As you probably know as well, sound travels in waves. 440 hz also means the 440 will hit your ear every second. This 440 hz is called the fundamental frequencey of the pitch. This is the pitch that you perceive (for the most part, we will get into that later). But, if you think that is all it is (which I call, with all due respect, The Magic School bus interpretation) you are wrong. If this is all that notes are about, what makes a tuba sound like a tuba and a flute sound like a flute? We call this timbre.
I touched on this in a previous post, but did not elaborate much. Timbre, also called tone color, is the quality that makes a sound seem to have come from a particular source, such as a voice or a violin or a piano. But what makes up timbre exactly?
A musical note is comprised of not one, but many frequencies. In most musical instruments, the overtones of musical instruments are generally multiples of the fundamental pitch. So, to go back to our example the A at 440 Hz, we would find overtones at or around 880 Hz, 1320 HZ, 1760 Hz and so on. These types of overtones are called harmonics. How loud or soft these overtones are are a big part of how we perceive the sound. There are other types of overtones as well. These are called partials and are not at any particular interval above the fundamental pitch. For a good note, there has to be little or no partials. The more chaotic the sound (i.e. the less harmonics and more partials in the sound), the less and less it sounds like a note and the more it begins to sound like noise.
The attack can be simply defined as how the note is started. There is a distinct difference, for example, between the sound of a piano and that of a trumpet. But, if you remove the attack from a recording of a note, it become much more difficult to tell the difference.
For the most part, the attack produces a loud burst of sound. The decay time is the amount of time it takes for the volume of the sound to be reduced down to how it will be for the majority of the note.
This is the main part of the note. As the name suggest, it is the part where the note is being sustained. It can be by the continued pressing of the piano key, or simply allowing the note on, say, a guitar, to continue to ring. How quickly the note reduces in volume is also taken into account.
This is like the attack, except at the end. It is the manner in which the musician releases the note. If you listen, you will notice that are distinct sounds associated with various instruments. It also includes what you might call the residual noise. Once a note is released, it doesnt stop instantly. The noise that hangs in the air is also included in timbre.
These are the slight changes in pitch that occur in the middle of the notes. This is different for each instrument. Although you may not pick up on it consciously, it is there none the less, and your brain picks up on it.
All things things are added together in your brain to let you know what instrument is playing. Remove one and it will make it harder to tell. Remove two and you may not be able to tell. Remove three and you have no way of telling.
This is really incredible. It is amazing to me that the brain picks up on so much, both consciously and unconsciously, to give us a more complete picture of the world around us. This is true not only in music, but in every aspect of life. I hope you have found this article informative. If you found it uninformative, well, thats to bad.