microtonal music, with varying systems being used depending on the situation. A common notation for quarter tones involves writing the fraction next to an arrow pointing up or down. Below are other forms of notation: A symbol with one vertical and three diagonal bars indicates a sharp with some form of alternate tuning. In 19 equal temperament, where a whole tone is divided into three steps instead of two, music is typically notated in a way that flats and sharps are not usually enharmonic (thus a C represents a third of a step lower than D); this has the advantage of not requiring any nonstandard notation. Time signatures Most music has a rhythmic pulse with a uniform number of beats—each segment of this pulse is shown as a measure. Time signatures indicate the number of beats in each measure (the top number) and also show what type of note represents a single beat (the bottom number). There may be any number of beats in a measure but the most common by far are multiples of 2 and/or 3 (i.e., 2, 3, 4, and 6). Likewise, any note length can be used to represent a beat, but a quarter note (indicated by a bottom number of "4") or eighth note (bottom number of "8") are by far the most common. Note relationships Dynamics Dynamics are indicators of the relative intensity or volume of a musical line. Rarely, even softer or louder dynamic levels are indicated by adding more s or s. While is called "pianississimo" and is called "fortississimo", these words (formed by adding an additional "iss") are not proper Italian. Dynamics are relative, and the meaning of each level is at the discretion of the performer or the conductor. Laws to curb high noise levels in the workplace have changed the interpretation of very loud dynamics in some large orchestral works, as noise levels within the orchestra itself can easily exceed safe levels. Articulation marks Articulations specify the length, volume, and style of attack of individual notes. This category includes accents. Articulations can be combined with one another and may appear in conjunction with phrasing marks (above). Any of these markings may be placed either above or below a note. Ornaments Ornaments modify the pitch pattern of individual notes. Octave signs 8va and 15ma are sometimes abbreviated further to 8 and 15. When they appear below the staff, the word