A curve connects two notes on the page. One curve means "let these two notes flow together smoothly." Another curve means "merge these two notes into one longer note." The two curves look identical. Misread one for the other, and the rhythm slips by a beat, or a phrase that should breathe in one stroke gets chopped into pieces. The most decisive moment of a melody can vanish into a missed beat, or two notes that should be articulated separately get glued together.
Slurs and ties are nearly identical curves on the page. But they give opposite instructions. One extends duration. One sets articulation. Telling them apart comes down to a single check — the pitch of the two notes at each end of the curve.
If the curve connects two notes of the same pitch — same line, same space — it is a tie. The two note values add together, and the result is a single sustained pitch lasting that combined duration. Two quarter notes connected by a tie sound exactly like a single half note.
If the curve connects two notes of different pitches — different lines, different spaces — it is a slur. The notes are played as one connected phrase. Their individual durations do not change. The slur is about how the notes are played, not how long they last.
The shape, slope, and length of the two markings are identical, so the curve itself reveals nothing. What matters is the position of the two notes at each end. Look only at the heads.
The Slur — Connect These Notes Smoothly
A slur groups two or more different pitches into a single unit. Composers draw slurs where the melody should flow without breaks. For wind instruments and singers, a slur means the notes inside the curve are played or sung in one breath. The performer does not take a new breath until the slur ends. For string instruments, a slur means the notes are played in one bow stroke. The bow keeps moving in the same direction across the entire slur without changing.
For piano and other instruments without breath or bow, a slur translates to legato articulation. Each note holds until the next note begins, with no audible gap between them.
A slur can be short, binding two notes together, or long, spanning many measures to mark a full phrase. The length of the slur typically follows the natural musical breathing of the line — one slur equals one expressive unit, one breath, one bow.
The Tie — Add the Two Durations Together
A tie connects exactly two notes. Those two notes must be the same pitch. The tie tells the performer to play one sustained note that lasts as long as the combined duration of both.
Ties appear in two common situations. The first is across a bar line. When a note's duration extends past the end of a measure, the composer writes the note in the last beat of one measure, the same note again in the first beat of the next measure, and ties them together. A quarter note at the end of one measure plus a tied quarter note at the start of the next measure sounds as a half note that crosses the bar line.
The second situation is within a single measure, when a duration cannot be written with a standard note value. A note lasting five quarter beats has no single symbol in 4/4 time. The composer might write a quarter + tied quarter + tied quarter, or a dotted half + tied quarter, to express the required length. Even a duration writable as a single dotted note (a dotted half = three beats) is sometimes split into a tied pair for readability when the rhythmic context calls for it.
The Tricky Cases
When both endpoints of the curve are visible on the same line of music, telling slur from tie takes only a glance — compare the two pitches.
The harder case is when the curve crosses a system break or page turn. The starting note sits at the end of one line; the ending note sits at the beginning of the next. Find the ending note on the new line, check its pitch, and the marking resolves — same pitch is a tie, different pitch is a slur.
Another case involves curves drawn on chords. A piano chord can have a slur on the upper voice and a tie on the lower voice simultaneously, with two separate curves on the same chord. Each curve must be read independently. Check the pitches at both ends of each curve.
It also happens that a slur and a tie are nested. A long slur binds a full phrase, and inside that phrase a single pitch sustains across two beats, drawn as a short tie under the long slur. The two curves overlap, but they do not contradict each other — one sets the phrasing, the other extends a duration.
Duration and Expression — Two Different Axes
The difference between the two markings comes down to what each one fixes.
- Slur = expression. The notes keep their original durations. One breath, one bow, legato.
- Tie = duration. The two note values add together. Phrasing is not affected.
The same curve shape carries two unrelated instructions. A curve over a melodic line that arches across different pitches is almost always a slur. A curve over a bar line, or over two notations of the same pitch written twice in a row, is a tie.
When reading a score quickly, the move is simple — see a curve, check the pitch at each end. Same line or space, the curve adds durations. Different lines or spaces, the curve binds expression. One look, and the two markings separate. Their identical shape stops being a trap.