Under a tie, also called ligature (from the Latin ligatura - band ) is understood in the music, the graphical binding of two notes of the same pitch.
The tie connects two consecutive notes of the same pitch, so that they sound like a single note. That is, at the first note attached with a tie second sound is not new hinged, but lengthens the duration of the first note. In this way, any note lengths can be achieved or extend notes over a bar line across - in this case, one speaks of " bandaging ". Thus, for example, a pedal point be set which continues over several clock cycles. A tie can also be set within a measure, if it helps, for example, can increase the clarity with syncope.
An alternative, shorthand notation for attached notes provides in many cases the dots.
The term denoted in square ligature, Modal and mensural an associated notation of several tones of different pitch.