 Unlike a graph, however, the number of semitones represented by a vertical step from a line to an adjacent space depends on the key, and the exact timing of the beginning of each note is not directly proportional to its horizontal position; rather, exact timing is encoded by the musical symbol chosen for each note in addition to the tempo.A time signature to the right of the clef indicates the relationship between timing counts and note symbols, while bar lines group notes on the staff into measures.