What is a note foreign to tonality?

A note foreign to tonality refers to a pitch that does not belong to the established scale or key of a piece of music. This can create tension or dissonance, as it disrupts the listener's expectation of harmonic resolution. Such notes are often used in various musical styles to enhance expressiveness and complexity. In tonal music, these foreign notes can be employed as chromatic notes, passing tones, or modal interchange.