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:
Key signature sometimes is this change indicated with a change of key signature; if not, the passage in the second key will not have a matching key signature. The Toccata and Fugue in D minor, BWV 538 by Bach has no key signature, leading it to be called the "Dorian", but it is still in D minor; the Bs that occur in the piece are written with accidentals. Keys which are associated with the same key signature are called relative keys. When musical modes, such as Lydian or Dorian, are written using key signatures, they are called "transposed modes". Exceptions to common-practice-period