A slur is a symbol in Westernmusical notation indicating that the notes it embraces are to be played without separation (that is, with legatoarticulation). A slur is denoted with a curvedline generally placed over the notes if the stems point downward, and under them if the stems point upwards.
Both accents and slurs relate directly to woodwind articulation...(and brass as well) since they employ a variety of tonguing effects [which are indicated by use of, "the correct form," of accents and slurs].[2]
[With bowed string instruments] A curved slur over or under two or more notes indicates that these notes are to be connected...Slurs are only partially indicative of phrasing; if an actual phrase mark is necessary (to unite several bow-strokes into a larger melodic idea), it should be notated above the passage with broken lines.[3]
The example below shows two measures in 6 8 with a slur for each measure:
Performance
Slurs mean different things for different instruments:
For wind instruments, the notes should be played without re-articulating each note (tonguing), except for the slide trombone (and other instruments that control the pitch with a slide), on which only certain kinds of combinations can be played with no tongue without making a glissando – thus "legato tonguing" is employed.[citation needed]
A slur can be extended over many notes, sometimes encompassing several bars. In extreme cases, composers are known to write slurs which are near-impossible to achieve; in that case the composer wishes to emphasise that the notes should be performed with as much legato as possible.
See also
Tie (music) - a similar symbol which combines adjacent notes of the same pitch into a single longer note