One of the most common mistakes arrangers make in their early days is to treat the brass (trumpets and trombones in the big band context) consistently as one section. In reality it often isn’t and the reason for this is simple. Ideally, the brass section would be one family of instruments with increasing bore sizes from the top down. In reality, we have a ‘choir’ of identical trumpets above another choir of trombones. Because of the difference in tone colour that exists between these two halves of the brass section it’s important to ensure a complete sound from trumpets and trombones in their own right as far as possible.
It’s true that the trombones in a five piece section can graduate from a medium bore lead instrument with a 7″ bell size followed by two larger tenor instruments, a large bore single-trigger trombone and the bass trombone. This setup works well and allows the brighter sound of the smaller trombone to cut through on lead. The trigger instrument is useful on 4th trombone in a five piece section, where open harmony is featured, because of its increased agility and resonance in the low register. Two bass trombones are also used.
Similarly, flugels can be used to give more depth to the bottom end of the trumpet section. The use of smaller Eb trumpets as lead instrument has never taken off in jazz.
A particular problem is caused by the fact that with one section stacked vertically above the other, the lowest trumpet in its weaker register is adjacent to the top trombone in its powerful register. In the simplest form of eight piece brass section writing, four trumpets and four trombones in close ‘block’ harmony, this won’t matter since the lead trombone will conveniently double the melody in the octave. Problems only arise when this effective distribution strays too far away from the middle of the orchestral range, especially when the phrasing is fast and agile. The lead trombone can enter the extreme high register causing balance and execution problems with dextrous parts. Again, the book gives an example of a complementary trombone section style which becomes necessary in cases such as this.
Another problem that is not peculiar to the brass section and affects all orchestration is that of acoustic clarity. Although our system of harmony has evolved independently, the vertical distribution of notes in orchestration is governed by the natural harmonic series (for example the series of open notes on any brass instrument). This means that chord functions have a lower limit for placement. Exceeding this limit implies a fundamental that couldn’t exist. The lowest practicable pitch for musical purposes is around 16 cycles. If you write out the harmonic series beginning on this note (it’s a ‘C’ two octaves below the second leger line under the bass clef) you can see the lowest position for the placement of each chordal function. In mobile writing there is a tolerance for transgressions but where the music comes to rest and at slow tempos care must be exercised.
There’s a useful diagram in the book but, for convenience, the first few notes of the harmonic series, beginning on C = 16 cycles, are: C, octave C, G, C, E, G, Bb, C, D, E, etc….. If you number these pitches from the bottom up, adjacent numbers give the ratios of the intervals: octave = 1:2, 5th = 2:3 etc. The 7th, 11th, 13th and 14th partials are out of tune with the equal temperament system that has been used since around 1550 A.D. Other minor discrepancies also occur. Once the 7th partial is reached the partial numbers are the same as the chordal functions: 7 = 7th etc. The 15th partial of the series on a C fundamental is B natural, equivalent to a lowered 15th (Cb) in a compound structure on C, which is consistent with information given in the book concerning the use of any note of the chromatic scale in any dominant 7th chord. The Bb and Cb have to be widely spaced or they’ll argue. The name Cb is preferred to attain a chromatically (and visually) ‘correct’ minor third between the top two notes of the 15th chord. Conventional harmony requires different letter names for each chordal note. An allowance is made for the repetition of the root or its altered form the lowered 15th.
The series shows that the lowest placement for the third of a chord is E on the first leger line below the bass clef and for the 7th it is Bb on the second line of the bass clef. The influence of the harmonic series also explains the tendency for harmonic intervals to become wider in the lower register. Despite the limit given above you wouldn’t normally use, for example, a C7 in close position with the above Bb at the bottom (‘last’ inversion). Volume has an effect on the lower limit for close position writing because loud playing thickens the timbre of the brass sound.
Of course, reality isn’t always as simple as this article implies. Music that uses percussive effects or tone colour in its own right may deliberately use the very muddiness we are trying to avoid to create sinister orchestral effects in the low register.
The most important voice leading considerations involve harmony at the level of triads and seventh chords. When the power and authority of the lower instruments of the big band are used effectively, there is considerable freedom to be enjoyed with regard to pitches used in the upper parts.
Even the relatively safe eight piece block style described above will run out of range if the instruments are taken too low. Sometimes, re-allocating the lowest trombone a root or 5th, instead of a 6th or 7th function, will rescue us but this causes a detached straggler in the trombones. Because the trombone section is perceived by the listener to be an independent section, it no longer has a four part sound in its own right and suddenly becomes triadic in style. The essence of the style of writing we are considering involves a series of harmonies of approximately equal ‘sock’ so that a sudden change to essentially three part writing with one doubled function can be a jolt to the senses (except at a point of repose when it can be very effective). Sometimes we can’t avoid it and in the ensemble the saxophones, as a coherent section, will be providing the complete four (or five) part sound in this register. The tenors must, however, exactly double the lower trombones or keep well away or clarity will suffer.
Occasionally the first trombone and fourth trumpet will share the same note in unison in an eight piece section, perhaps to enable the root to appear in the fourth trombone part on a sustained or accented note. Use your own judgement based on the choice of available options with all the above guidelines in mind.
The book contains some examples of voice leading problems that can arise in the four trumpets/three trombones brass section, where it’s often necessary to move the lowest trombone out of its strict close position block placement. There are occasions when traditional ‘rules’ will apply here. Watch out especially for ‘exposed’ octaves and 5ths between the lead trumpet and third trombone and for parallel 4ths between the second and third trombones. Parallel 4ths are not good between the ‘bass’ and its adjacent note above. The brass section will be perceived by the listener to be an independent system so we can’t use the existence of the string bass underneath it all to get us out of trouble. Nice try. (Reminder: ‘bass’ doesn’t always = ‘root’.)
We’re discussing run-of-the-mill voicings here not special effects where any form of parallelism might be desired.
The solution to many of the difficulties we face often involves writing the trumpets in close harmony and the trombones in open harmony, especially at slow and medium tempos. This way the trombones can always achieve the ideal of getting a complete sound in their own right, even with a three piece trombone section. More care over voice leading is needed in open harmony since the connections are not as automatic as they are in close position writing. Occasionally (but not often) traditional rules are sacrificed in four part open position to achieve a series of harmonies of roughly equal tension. This problem doesn’t occur with five piece sections where voices move to the nearest adjacent note to avoid crossing of parts (which can be justified where a distinct advantage is gained).
With five trombones, with or without sax doubling, the lower brass are capable of attaining considerable strength and passing notes in the trumpets can be accommodated in situations where the trumpets and trombones have contrasting mobility. Yet again the Kenton band is the ultimate listening guide on this issue. Taking the risk of clashes to the limit gave this band one of its most distinctive characteristics.
There is also the risk of trombone execution problems in the lower register and muddy writing with awkward melodic lines in the voicing becomes even more objectionable when compounded by the relative clumsiness of the slide trombone when playing at speed in the low register.
Care must be taken to avoid acoustic problems when using extensions and altered notes. It’s possible to use both the perfect 5th, in the lower harmonies, together with the raised or lowered 5th in the upper harmonies where there is sufficient vertical separation. In such cases the raised and lowered 5th become the lowered 13th and raised 11th respectively. Overlapping voiced sax section fills will generally conform to the corresponding notes in the brass at each point in the harmonies on sustained notes. Because chordal rhythm playing by the guitar and piano are in the middle harmonies, the altered 11th and 13th notes need not necessarily be marked on these parts.
The 9th, and especially the 11th and 13th functions in the trumpets will not always be duplicated in the octave by the lower instruments, which will have a marked tendency to remain in the four or five part chord domain. This advice goes against common practice and it is admitted that this is a complex area in actual music. In my opinion the need for acoustic clarity requires more careful consideration of the problem than is often the case and what we see is a tolerance to situations, which isn’t quite the same thing as evolution. I wouldn’t, for example, use a 7th chord with raised 9th and use the raised 9th again an octave lower below the third of the chord. It’s done and some think its cool but I don’t like it. An exception would be where the raised 9th is an octave duplication of the melody (but don’t sustain it too long).
When the root is omitted a ninth chord becomes a m7(b5), a flattened 9th a dim7 and a raised 9th a dim chord with a natural 7 (etc…etc…) which changes everything (but you’ll still have to consider the rhythm bass part). The book mentions the ambiguity in traditional harmony where so-called 13th and 11th chords are intonationally identical to ‘secondary’ seventh chords when in four part form. Traditionally, a G13 in four part form might be f-a-c-e, identical to Fmaj7 for the jazzman. If we place the F of this chord below the bass clef it is too low when the root is added underneath but the four part version of the chord works fine in open harmony (F-C-A-E) since we can call the F the root. If we change the rules we don’t have to break them. A more common four part form of the 13th chord in jazz would be 3rd, 7th, 9th and 13th. (We need the third and the seventh to identify the seventh chord and the 13th requires the support of the ninth.)
It can be desirable to have an exact duplication of the trumpets in the trombones providing the brass section doesn’t drop too low. Such cases always involve the absence of the root in the brass section itself when using higher extension chords. Applications include ensemble work where the lead trumpet, lead trombone and lead sax are all cooking along with the melody. Even the baritone will often have the melody at the bottom end. This style of writing also makes the use of extreme high register brass section writing for the trombones more acceptable since they have the total support of the trumpets and saxes. It’s a style that ideally suits low to medium speed soloistic passages for the orchestra where pedantic voicing would spoil the free-flowing melodic effect.
There are also stratified effects, described in detail in the book, where the trumpets play a three or four part stratum of thinned down harmonies and the fuller harmonic bulk is provided by the trombones (plus saxes in the ensemble). In such cases the 6th of a block trumpets chord (for example) might become the 13th when combined with the lower instruments.
The trumpets are also sometimes written in open harmony when the lead goes into the extreme high register. A sustained maj9 chord could have the trumpets playing root, 5th, 9th, 6th, 3rd from the top down. Mobile voicing leading into this chord would have a matching distribution. The semi-open (wide) distributions shown in the book intermingle OK with 4th interval chords of the above type.
The book also gives examples of five part writing for brass sections, where practical limits have to be placed on the number of instruments used. The rest become redundant.