curved line connecting 2 more notes different pitches
Tie (music) In music notation, a tie is a curved line connecting the heads of two notes of the same pitch and name, indicating that they are to be played as a single note with a duration equal to the sum of the individual notes' values. A tie is similar in appearance to a slur, however slurs join notes of different pitches which need to be played independently, but seamlessly.
Curvature One way is geometrical. It is natural to define the curvature of a straight line to be constantly zero. The curvature of a circle of radius R should be large if R is small and small if R is large. Thus the curvature of a circle is defined to be the reciprocal of the radius:[2]