Universal key fractions (e.g. an A natural in the scale above becomes ) or, more commonly in written text, by inserting an accidental before the number (e.g. the same note becomes 5 or 4). In music theory aimed towards jazz and popular music, all triads are represented by upper case numerals, followed by a symbol to indicate if it is not a major chord (e.g. "m" for minor or "ø" for half-diminished): When representing the triads rooted in a minor key, accidentals are used to indicate the chromatic alteration from the assumed major key roots indicated by numerals that don't have accidentals:
Off-key note in jazz. The opposite of off-key is on-key or in-key, which suggests that there is a well defined keynote, or reference pitch. This does not necessarily have to be an absolute pitch but rather one that is relative for at least the duration of a song. A song is usually in a certain key, which is usually the note that the song ends on, and is the base frequency around which it resolves to at the end. The base-frequency is usually called the harmonic or key center. Being on-key presumes that there is a key center frequency around which