Throughout the world, there are many different notation systems in music. In Western Europe and North America, we use a 12 tone system with the musical alphabet. To understand the 12 tone system, we first need to understand how we measure the distance between two notes. There are two main distances used in our system, there are tones and semitones. The easiest way to see and understand tones and semitones is on a piano. A piano is made up of white keys and black keys.

And a tone is the distance between two white keys with a black key in the middle, or between two black keys with a white key in the middle. a semitone is our smallest unit of distance, which is between a white key and a black key, or between two white keys where there is no black key in the middle. All scales in music are simply a pattern of tones and semitones that repeats The most common one is the major scale, which goes to tone, tone, semitone tone, tone tone semitone on a piano, if you start this pattern on C, there's no need to use any black keys because the pattern is built right into the keyboard of tone, tone, semitone tone, tone tone semitone. If you start the pattern on any other key, however, you need to use the black keys to maintain the pattern. This is why we have sharps and flats to make up the 12 different keys inside of the system.