With one more scale tone than present in the western diatonic scale, it is not possible to notate music in the octatonic scale in any conventional occidental key signature, without the use of accidentals. In any conventional key signature, least one of the semitone steps must be written as two notes with the same letter / on the same line or space on the staff. (That is, there must be at least one note that regularly appears with two different accidentals.) There are usually several equally succinct combinations of key signature and accidentals, and different composers have chosen to notate their music differently, sometimes ignoring the niceties of notation conventions designed to facilitate diatonic tonality.