Tuesday, August 18, 2009

Optical note spacing

I recently obtained a book by Herbert Chlapik entitled Die Praxis des Notengraphikers, or (roughly – my German is tenuous at best!) The Practice of the Music Engraver. With a little help from Google Translate, I'd like to present his description of optical note spacing. Neither Sibelius' nor Finale's spacing algorithms take this into account, so every instance must be corrected by hand.

Optical Compensation

Every typesetter or graphic designer understands that the different letters, especially capitals, require their typographical design be taken into account. It is an optical phenomenon that
uniform spacing between letters in certain combinations creates precisely the opposite impression. Only kerning – introducing a a small expansion or contraction between letter pairs – creates an optical illusion that suggests complete uniformity.

Though unkerned pairs in may be perceived as ugly, the readability is not affected much. This may in fact be the case with music notation as well. The widely disparate forms of musical symbols and their position to each other tends to cause irregularities which are disproportionately larger than those found in a line of text. The spacing between the characters is defined by the rhythmic structure and must assist the musicians' spontaneous comprehension. Notes must therefore be spaced not just according to their calculated position, but also so as to be visually correct.

An optical compensation must be made in the following situations:

1. When stem-up and stem-down notes are next to one another.

2. If there is a (lower) stem-up note after a rest.

3. Cross-staff beaming [this is a subset of the first case]

As examples 1–3 show, one does not calculate the distance between the notes, but between the stems. This seemingly-erroneous calculation of the note spacing causes the optical illusion that looks correct to the eye.

4. Large intervals.

Reduce the space between large intervals by about a third.

5. For the space between stem-up short-value notes and the barline.
The space between the last note and the barline should be slightly larger than the exact calculation.

Only in multisystem situations is the optical compensation improper because it can cause distortions in the other voices.

[Here he discusses vertical spacing between staves. In short, the uppermost and lowermost characters on adjacent staves define the closest possible distance between them. Any extra space left over after all the staves are spaced may be equally distributed.]

Since it is impossible to show all variants of the optical compensation, examples must be limited to the essentials. The trained eye can find other situations where a slight compensation would give a better visual result.

The translation (such as it is) is mine, but the text and images are copyrighted 1987 by Ludwig Doblinger (Bernhard Herzmansky) KG, Wien – München. Published here under the fair use provision of section 107 of the US Copyright Law.

1 comment:

Ashley and Drue said...

Lilypond uses optical note spacing in its engraving. They reference it in the beginning of their Learning Manual.