In music, a scale is a set of notes in order of their pitch (that is, their frequency). If the scale starts with the note which has the lowest pitch and goes up to the note with the highest pitch, the scale is called "ascending". If the scale starts with the note which has the highest pitch and goes down to the note with the lowest pitch, the scale is called "descending". Scales are often the same both ascending and descending, but this is not always true. Very often, a scale is defined over an interval (such as an octave). The most common scales use intervals of five, six or seven different notes.