I would like to warn the reader that this blog contains opinions that may not be shared by all.
The habit of joining together with other musicians during performances is as old as music itself but the systematic arrangement of instrumental groups, that we now call ‘orchestration’, is comparatively new. It is a feature of formalized European music, other native cultures following a different path, as they do to this day.
The Church used to be virtually the only source of cultivated musicianship and a composer would be obliged to use whatever group of musicians happened to be available, leaving no one aside, and find them all something to do. This pattern continued even when wealthy patrons arrived to help composers pay the rent. The requirements of liturgy also gave shape to early music.
Even when the orchestra, as we now recognize it, began to take shape, a keyboard was still used as the centre of everything, the keyboard player becoming, in effect, the conductor. Combining the keyboard with other instruments limits the keyboard styles available, especially within contrapuntal works, which were common. Anything that emphasizes vertical structures, together with the correspondence of simultaneous down-beats and accents, will reduce the contrapuntal quality of music. A piano or harpsichord would also have helped to keep amateur musicians in tune. They also assisted the assimilation of the music from the point of view of listeners for whom the experience of aurally ‘scanning’ large groups of musicians, spatially separated and sometimes playing different but complementary roles, would have seemed rather strange. We take it for granted nowadays.
Improvements had also taken place in the manufacture of musical instruments, partly to ensure that they kept pace with the increase in virtuosity which, too, increased possibilities. (The clarinet was a recent addition to the orchestra in Mozart’s time).
The string section, because of its huge range and flexibility, became the force that, usually, bound everything together, other instruments being used to give occasional variety and to provide colour.
The orchestra as we know it
When virtually any instrument would be available, as a matter of course, composers could write in a style that matched each instrument’s characteristics. Instruments no longer had to cover a multitude of sins. The majority of attack forms are achievable on most instruments but some instruments lend themselves, for example, to smooth cantabile playing better than others. Woodwinds are capable of lightness and dexterity and feel more at ease when playing at an extremely low volume. Any brass player knows that maintaining a good quality of sound whilst retaining good intonation and clear articulation, at low volumes, requires a lot of practice. It also requires physical and mental flexibility following prolonged loud passages. On the other hand, brass instruments can provide heavy attack forms better than other wind instruments. Woodwinds in the high register sound relaxed but the listener is always aware of the effort involved in playing high notes on brass, which imparts a feeling of power and even aggression.
There is also a natural hierarchy regarding the vertical placement of instrumental sections. It usually feels unnatural to place sustained woodwind harmonies below brass harmonies because of the woodwinds’ comparative lack of sonority but it might, conceivably, be done for special effects. The woodwinds frequently double the brass either in the same register or in the octave (or double octave). Exact doubling is preferred to avoid ‘stray’ notes standing out at the expense of the other parts of harmony. In other words, it will sound as if the parts were supposed to be the same but something went wrong. As sections deviate more in terms of mobility and accent, more freedom will be available.
Harmony, melody, rhythm and instrumental resource are a composer’s most obvious tools but differing degrees of transparency and density are available. Density is also a matter of style; some composers habitually used transparent orchestration, perhaps due to the fact that they had tidy minds and disliked ‘clutter’. Density can occur incidentally as a result of the failure to handle combined orchestral sections systematically or because the placement of instrumental parts pays insufficient heed to acoustic requirements. Congested voice leading can also bring it about.
I myself have always been less inclined to double individual parts in orchestration in order to obtain different tone colours, preferring a purer style. Nevertheless, individual ‘lines’ are sometimes intended to stand out where the part has a clearly defined shape or tunefulness or where, perhaps, it is thematically linked to something occurring elsewhere in the piece but, generally, I prefer ‘section-by-section’ writing because instruments of a similar tone colour tend to cohere. Anything they perform simultaneously will be perceived to be linked together, leaving the ear of the listener to expect similar sounding instruments to form some kind of acceptable structure in their own right.
The English-style brass band is a good example. With the obvious exception of the trombones, all instruments, from the Eb soprano down to the BBb tubas, belong to the same family, raising the temptation to break down the sections and to treat the band as one whole unit. It is often done to allow arrangements to be playable by varied instrumentations as, for example, when members were absent because of industrial injury or illness or because they were involved in trade union activities. Top level bands will always have a full lineup, where so-called ‘special’ arrangements may be used.
I never use double-stops in the string section, especially with the cellos and basses, where they will sound ‘muddy’, because of factors within the instrument itself*, and where they are likely to conflict with trombones in the same register. It is better to reserve them for solo passages.
Whereas fretted instruments, such as the guitar, are tuned to equal temperament, the tuning of unfretted instruments is influenced by just intonation. Some tuning techniques used will naturally lead a player in this direction. This subject is part of the wider problem of acoustics, which requires knowledge of the mathematics involved for a complete understanding.
The manner in which the two methods are actually combined in music is a different matter. For example, when moving in semitones from c>d the c# will be slightly higher in pitch than its enharmonic equivalent, the note db, will be when moving downwards in the opposite direction, d>c. These are interpretational, not acoustic considerations. Notes moving chromatically ‘lean’ towards the note of resolution. Fixed pitch instruments do not enjoy this luxury. We trombonists do it all the time.
As the music of the 20th century evolved, composers sought to extract new sounds from conventional instruments, eventually being rivalled by electronic effects, which were also combined with the orchestra. Music notation programs now offer some very authentic sound fonts which emulate live instruments very well but there is an important difference: each part of an orchestration may be played by several instruments, giving considerable weight to each part. This is especially true of the strings, particularly where ‘Hollywood’ style divisi styles emulate jazz and big band scoring. The technique requires careful handling.
A typical 20 piece Radio orchestra string section comprises 12 violins (6 first, 6 second), 4 violas and 4 cellos. Frequently only one acoustic bass will be used. The block harmony style resembling an eight piece big band brass section requires more strings on the top part (melody) than on the other parts, distributed: violins 6,2,2,2,/violas2,2,/cellos2,2 . The fifth voice down (2 violas in this example) will also feature the melody in the octave. Dividing the strings into violins 4,4,4, violas 4, cellos 4 gives a four part block style with the melody in the octave. Here, the powerful support of the cellos playing the melody obviates the need to increase the number of violins on the top parts. Strengthening the melody helps to paper over the cracks that are often present in each part, melodically, in these block scoring styles for strings. With the big band, with one player to each part, the problem is less acute.
Complex divisi writing is divided by desk. There are two players to each desk (music stand).
The book illustrates examples of various string styles, including those that are more typical of string writing.
* I doubt that anyone fully understands the effect of two or more notes resonating within the body of stringed instruments.