Clear linear motion is an important element in polyphonic music. In most orchestral music vertical sonorities are the result of several lines heard simultaneously, and the forward linear movement creates the harmony. Primary lines must be distinguished from subordinate lines and orchestrated in a more prominent fashion. Important melodic lines can either be assigned to instruments with more vivid tone colors and penetrating power or placed above other pitches in the harmony. Because they are the most distinguishable to the ear, the top and bottom lines are of principal importance.
In highly contrapuntal music each part must maintain independence from the others, and preserving the clarity of each line is the primary concern in scoring. Arranging a fugue by J. S. Bach for a mixed chamber ensemble is an excellent exercise for applying techniques that help preserve linear independence, including the following:
1. Assign single instruments of dissimilar tone color to each part, and keep the texture thin.
2. Use octave transposition to prevent lines from overlapping too much in the same register, or double lines in different octaves.
3. Apply both of these techniques, using contrasting choirs of similar instruments on different parts.
4. Mark articulations very carefully so that the entry of a new part is a noticeable event in the texture. Marking each entry of the same subject with identical articulations greatly enhances the effect of imitation and saves rehearsal time.
5. Use dynamic markings consistently with crescendos and diminuendos to control the intensity of each part. This helps the players identify their roles.
6. In dense textures new entries may be highlighted with pitched percussion This technique brings them to the foreground without adding mass.
7. Another way to differentiate motives or themes from surrounding lines is to use short note values in one part and sustained tones in another part. This is especially applicable when combining two or more of the same instrument with different musical functions.
There are numerous ways of differentiating between the importance of lines in a composition, including the following:
1. Assigning the prominent line to a single instrument with a distinct timbre is the simplest and one of the most effective ways of differentiating it from the background.
2. Doubling with the same instrument at the unison can create intonation problems, particularly with a unique timbre such as the oboe. This problem can be alleviated by using three or more of the same instrument on the line.
3. Doubling at the octave with the same instrument creates an interesting new tone quality and does not create potential intonation problems. The effect is one of greater penetration rather than greater mass. The soprano line is more effective doubled one octave above; the bass line more effective one octave below. The latter is a standard procedure for cellos and string basses.
4. Two or more different instruments on a line, either in unison or at octaves, can create a most colorful sound. The flute, clarinet, horn, and bassoon blend well with most other instruments and are easily absorbed. The oboe and trumpet tend to assert their tones. The tuba adds considerable mass to any combination.
5. Woodwinds are usually placed above the brass in combination, where they strengthen the upper partials. Placed among the brass, they lessen the brilliance without adding strength or color.
6. Combinations of woodwinds and strings lend resonance and body to the string tone and soften the winds. Except for the horn, brass and strings do not blend well.
7. A section of strings playing together is not necessarily much more powerful than a single instrument, but it is richer due to the chorus effect. The upper strings in their highest register have the capacity to pierce any texture except the forte brass and percussion.
Subordinate lines need to be scored in a contrasting hue, or pale color, in a controllable range of the instruments assigned. Several options for scoring secondary lines follow:
1. A group of similar sounding instruments which are easily covered assigned to each subordinate line can provide an innocuous background. Second violins, violas, and cellos are frequently used in this capacity, as are the clarinet and bass clarinet. The number of performers lessens the degree of individuality and tends to average out the articulations.
2. A group of dissimilar instruments on the line in one or more octaves is slightly more noticeable, depending upon the blend of voices chosen.
3. Single instruments assigned to the accompanying lines with similar sonorities stand out even more, providing clarity.
4. Subordinate lines can be given to single instruments, each with a unique timbre, for the strongest effect. This is the most interesting, yet problematic, solution due to differences in balance and blend. Whenever blend is important, the range of the instrument is a critical factor. Placing an instrument in an extreme part of its range frequently prevents a good blend and introduces problems with intonation.
Constant bright color in the ensemble begins to wear on the ear, as does rich food on the palate. The double reeds have a unique and often strident tone, but are not powerful and assertive. One factor that makes an instrument stand out or attract attention is the amount of vibrato the performer uses. Because the flute and strings generally are played with considerable vibrato, they are noticeable in a texture. The table above differentiates between the strong voices in the orchestra, and those easily covered.
Drastically terraced dynamics should not be used to compensate for improper balance. It is, however, important to give players a clue as to their role in the ensemble by including some dynamic marking at all times. Articulations and phrasing should also always be included. One means of giving the background less force or weight is to use notes of shorter duration.