Eleanor Selfridge-Field and Edmund Correia, Jr.
© 1994 Center for Computer Assisted Research in the Humanities
Reproduced by the IEEE Technical Committee on Computer Generated Music by permission

Category 4. Ties, Slurs, Beams, and Stems

Slurs and beams posed great difficulty to early music notation programs. Although in our mind's eye we imagine both to be geometrically regular, slurs and beams in traditional typesetting assume a great range of different configurations. When slope, vertical orientation (up or down), and extent are taken into account as elements of a three-dimensional array, the number of combinations encountered in ordinary circumstances reaches well into the thousands.

Beams are governed to some degree by local custom and house style. For example, in the French style note stems do not cross multiple beams, while in the English style they do. In some systems the secondary beams covering long strings of sixteenth or thirty-second notes are segmented to facilitate reading. The implementation of this style obviously requires more programming effort than simply running beams in parallel across the affected group.

There are many contextual idiosyncrasies involved in the treatment of slurs and beams. If within a group of notes attached to one beam the pitches are widely spaced (as happens, for example, in many virtuoso violin parts), the beam may create a barrier between the higher and lower notes, with stem directions varying accordingly. In keyboard music written on the grand staff, a single beam may connect notes displayed alternately on each of the single staves.

These situations have analogues in the domain of slurs. The shaping of slurs over notes with an exceptionally large span, or with stems in reverse directions, or displayed on two staves may involve U curves and S curves that exceed the provisions found in standard graphics palettes.

Ties are not prone to the same problems of displacement as slurs, but the attachment of slurs and ties to the same note poses increased constraints on the placement of both.

It is a widely held but mistaken assumption that a curved line connecting two notes on the same pitch is necessarily a tie (for exceptions, see Bach's St. Matthew Passion).

Since the resolution of problems in this category is somewhat at the discretion of the user, we are showing multiple examples.

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