خط اتحاد

In music notation, a tie is a curved line connecting the heads of two notes of the same pitch, 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 (legato).

Ties…are a notational device used to show the prolongation of a note into succeeding beats, as opposed to a repetition of a note. … Our modern tie-mark, first systematically used in the early sixteenth century [Baroque music], is a curved line that connects the two successive note-heads indicating, together, the total time value desired. … Ties are normally employed to join the time-value of two notes of identical pitch.]

Ties are normally placed opposite the stem direction of the notes, unless there are two or more voices simultaneously.

The tie shown at the top right connects a quarter note (crotchet) to a sixteenth note (semiquaver), creating a note ​۵⁄۴ as long as a quarter note, or five times as long as a sixteenth note—there is no single note value to express this duration. However, in some cases one might tie two notes that could be written with a single note value, such as a quarter note tied to an eighth note (the same length as a dotted quarter).