All Western music theories are built on a chromatic scale. You can think of it as the 12-tone musical alphabet, because it contains all the raw data we use to construct more complex things like all other scales and chords. Just as the English alphabet is not used directly, but rather with the application of grammar, chromatic scale must be organized into more useful structures. Some composers have used the chromatic scale as for a type of sharp, atonal music, but this is not the norm.
Seven letters are used. Going back several hundred years to Germany, Austria and other European music centers, the first seven letters of the alphabet are used to create a framework for the large scale. Although language may be different, the idea of the first seven letters remains consistent and today we use ABCDEFG. These letters refer to notes (tones) and when played as CDEFGABC a large scale is created (see my related article). Think of the letters as symbols that represent sounds.
To name all 12 notes, we must add sharps (#) and flats (b). These are symbols that raise or lower the pitch (tone) of the original seven notes. For example, A # is a half step (halftone) over A natural. Ab is half a step lower than A naturally. Think: Sharp = plus 1, Flat = minus 1. Music theory is easiest to understand on a keyboard or a single string of guitar. If you just play the white keys on a keyboard, you get the natural notes ABCDEFG. Put the black keys in order with the white keys and this is what you have:
AA # BCC # DD # EFF # GG # A (cycle starts again but higher)
Descent, with apartments:
A Ab G Gb FE Eb D Db CB Bb A
How come two notes will not be sharp or flat? This is because we use a 7-letter system to describe 12 notes. The 7 letters work well for large scales, as there are 7 notes on a large scale. out the remaining 5 notes that are not on a large scale, we use sharps or flats (7 + 5 = 12). There are 7 letters, but we only need to name 5 more notes, so that is why 2 do not require a sharp or flat.
Practice playing chromatic scale on your instrument and naming the notes aloud. Use sharp ones that go in one direction and flats in the other, then turn them over (list flats: A Bb BC Db etc.) The chromatic scale is the basis of any other theory and you have to understand it to make sense of more complex ideas . Remember which notes do not have flats or sharp. Feel one-harmonic (same sound) equivalents:
A # = Bb
B # = C
C # = Db
D # = Eb
E # = F
F # = Gb
G # = Ab
Tips and warnings
The chromatic scale is the basis of all music based on the Western (European) music system. Also called the equal temperament system, because the notes are all equally distributed.