What are Pitches?
Now we know how much a wide variety of pitches can help the sound of music. But what exactly is pitch? We know that musicians can produce both high and low notes, but how exactly does it work? Well, remember what we discussed in Lesson 1? Sound is simply vibrations of air. We've established that there is an infinite variety of vibration possible, creating an infinite variety of sound. But that still doesn't answer our question of "What are Pitches?".
Well, consider this: the main chamber music instruments all have strings, right? Well, a string instrument player can raise the pitch of his/her instrument by moving his/her fingers to shorten the string! A pianist can raise the pitch of his/her instrument by playing a key connected to a shorter string! So, a shorter string must cause a higher pitch, and a longer string must cause a lower pitch! Maybe you've tried this with a rubber band before: if you pinch off the rubber band and pluck it, it will vibrate; causing a high pitch to occur. If you don't pinch the rubber band and just pluck the entire band, it will vibrate and cause a lower pitch to occur. This works in the same principle as the chamber music instruments
Great! Now we know how to create a higher or lower pitch. But
what exactly is happening? Well, every time a musician plays a
note, his or her string is vibrated very rapidly. In other words,
the string moves back and forth almost inconceivably fast (the
violin's A string vibrates at 440,000 times per second!). A longer
string will vibrate more slowly than a shorter string. Perhaps
you've experienced this with a jump rope. A single person jumping
rope can get his/her rope to go very quickly. This is similar to
the vibration of a short string. A jump rope held by two people
standing far away will not travel nearly as quickly as the single
person's jump rope. This is similar to the vibration of a long
string. So, fast vibrations must correspond to higher pitches, and
slow vibrations must correspond to lower pitches.
OK, so we have some idea of what pitches are. It gets a little more complicated, though... In music, only a select number of pitches are ever played. Why? Well, music has just evolved over thousands of years to only incorporate a select number of pitches. You can bet that it has evolved the right way, too, if you've ever heard an out-of-tune viola. An out-of-tune instrument plays pitches that are slightly off from what they should be. For example, if an instrument was supposed to play a pitch vibrating at 440,000 times per second, it might vibrate at 441,000 times per second. This creates an awful sound, almost as bad as those random notes from Lesson 1.
So how exactly did musicians decide to use only a certain number of notes? Well, that brings us to a funny story involving the great composer Johann Sebastian Bach. After the end of the Renaissance, there was some debate over the best notes to be used in music. For example, Indian music uses 22 notes per octave. Well, J.S. Bach was a strong supporter of using 12 notes per octave, which is the system still used today in Western music. To prove that his system was the best, Bach wrote a prelude and fugue in 24 keys: two on every note (both major and minor). Evidently, Bach made his point and so his system of 12 notes per octave is still used today.
In addition to these 7 pitches, there are 5 more pitches that
can be represented by adding a '#' or a 'b' symbol to each note
(e.g. A#, Bb). These symbols are referred to by a group as
"accidentals". An accidental can be cancelled out by using the
"natural" symbol, which is unfortunately not a member of ascii
text. We have put together a little display of the most common
accidentals used in music. There are more complex symbols (such as
the double flat or double sharp) but these are rarely used.