How does a diatonic scale differ from a chromatic scale?

The primary difference between a diatonic scale and a chromatic scale lies in the number of pitches used and the intervals between them.

• Diatonic Scale: This is a seven-note scale that forms an octave using a specific pattern of five whole steps and two half steps. It serves as the foundation for most Western art music, with the major and minor scales being the most common examples. Because it uses only seven of the twelve available pitches in an octave, it establishes a clear sense of key.12
• Chromatic Scale: In contrast, the chromatic scale consists entirely of half steps. It encompasses all 12 pitches within an octave, corresponding to all the white and black keys on a piano keyboard.312

While diatonic music may occasionally incorporate "chromatic tones"—notes that fall outside the established diatonic scale—the chromatic scale itself treats all 12 semitones as equal, a concept that became increasingly prominent in 20th-century compositions, such as those by Arnold Schoenberg.12