Passing notes are typically used to fill out the interval of a third, and on occasion a larger interval, such as a fourth. As is the case with any type of melodic decoration, passing notes can be used effectively on both accented and unaccented parts of the beat. When used on an accented part of the beat, the dissonance introduced by the passing note is more prominent. Passing notes that belong to the major or minor scale of the key being used are called diatonic passing notes. Passing notes can also be chromatic. A chromatic passing note borrows from those notes of the chromatic scale not belonging to the diatonic scale of the key. The most typical use of a chromatic passing note is to fill in the interval of a major second between the voice parts. This creates a moment of tension as the chromatic note then resolves either upward or downward to the harmony note, as the case may be. Where the chromatic note occurs as a rising passing note, it is typically notated as a sharp. Where it is being used as a falling passing note, it is notated as being a flat. This is because these symbols naturally reflect the directional tendencies of the passing note.