OK, you should by now be practicing your major scale. There is a lot in that scale, and we will be expanding on that later. For now we need to learn a bit about the mathematics of music. Don’t worry, it’s easier than multiplication tables, and it will be well worth the effort.
Refer to the following chart as you consider this explanation. Lets look at the musical alphabet again A-B-C-D-E-F-G. Now consider assigning numeric values to these letters. A will be number one, B will be two, C will be three, and so on. So if we wanted to play several notes in succession, we might call for an A-D-E progression for instance. With our numbering system, we may also refer to this progression as a 1-4-5 progression. A is one, D is a fourth interval from A, and E is the fifth interval from A.
Now let's add the concept of keys. In simple terms, the key of a succession of notes refers to the lowest note, or bass note in the progression. If we are playing in the key of A, then A will be the lowest note, or bass note. However, we may want to play in the key of B. Then our progression would look like this.
In the key of B, the B note is the first interval, C is the second interval, D is the third interval, and so on. If we are in the key of C, then C is the first interval, D is the second interval, and so on.