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The Art of MIDI Orchestration

By Jerry Gerber

Introduction

The principles of orchestration have been presented in several classic texts by Kennan, Adler, Piston and others. In what ways do these principles apply when considering the virtual orchestra?

Just as an acoustic score's realization will not be identical when played by two different orchestras, a MIDI-realized score also is interpreted by what hardware and software are used in the studio and what level of musicianship is brought to the production process. Though musicians use various hardware and software platforms to realize their ideas, the core issues are universal: How to achieve the most musically expressive score with the technology you have at your disposal. We'll focus on the many details which help bring expressiveness and intention to our music.

While there have been many musicians who consider MIDI as a mock-up for what is meant to be performed by a live ensemble, this perspective often means that while sequencing a composition many shortcuts are made and many decisions that ought to be made are not. For those composers who are convinced of the expressiveness of MIDI as an artistic medium in its own right, this article will address some of those techniques.

Like any medium, MIDI has its strengths and limitations. In the acoustic world, much of what we accept as part of the musical experience involves many sounds that are not really musical at all; fingernail noises against strings and the sound of breath and mouth clicks for example. These non-musical artifacts are so deeply accepted in our musical culture that we simply ignore them and focus on the music itself. But when a new medium arrives we become very critical and sense shortcomings very quickly. This makes it all the more important to understand how to infuse MIDI instruments with musicality, expression, gesture and intention. It means understanding your sounds and samples and exploiting all of the parameters that can lead to deeper expression. Very satisfying musical results are quite possible with MIDI, and the situation is improving with every new generation of hardware, software and the ongoing evolution of sample libraries.

Orchestration styles change. The orchestrations of Stravinsky are very different from that of Mozart's, as are Copland's from Mahler's. Since the virtual orchestra defines a medium, but not a musical style or genre, this divergence of approach to orchestration remains true in the virtual world as well. We've seen music concrete, sound design, electronica and the virtual orchestra evolve from electronic music and we will continue to see new genres and styles find a home with this new medium. For those composers interested in taking the principles of orchestration and applying them to MIDI, the concepts of orchestral balance, blend, transparency and orchestral weight still make sense, we must still be concerned with primary, secondary and tertiary materials, and knowing how to score a good tutti is useful. We will return to these concepts later in the article.

It is sometimes difficult to separate orchestration from composition. Many of the timbre choices an orchestrator makes has to do with planning how the piece's structure evolves, and orchestral textures are often employed to contribute to the form of the composition. I find Walter Piston's idea of the seven textural types very useful. Please see his book on orchestration for a complete explanation and examples. 

In the electronic orchestra, even just one synthesizer timbre can be a complex texture in and of itself, with multiple amplitude and filter envelopes, dynamic panning and modulation of harmonics synchronized to tempo. This is new territory and the point where classical orchestration is not going to be of much help. The virtual orchestra gives us new options: We can use samples of acoustic-based instruments to orchestrate our music and/or we can use sounds that cannot be duplicated in the acoustic realm; these sounds are often complex, sometimes with non-whole integer harmonics and often with a built-in rhythmic pulsation produced with sample-and-hold, LFO or other devices. When using complex electronic sounds, listen to the harmonics and rhythmic patterns that are present. This can provide a hint as to how to proceed to integrate this timbre into an orchestral setting.

Designing the Ensemble

One of the great joys of MIDI is that it gives the musician the capability to pick and choose instruments that, in earlier times most likely would not have been heard together in an ensemble. In my Five Songs on the Poetry of Tu Fu (Ottava 02-006) I designed an ensemble using samples of Chinese percussion and other instruments from that region of the world, a flute from South America, an Irish harp, Western strings and sounds of water and wind.

By going through our synthesizer patches and sample libraries we create a specific ensemble for the needs of the piece. Later on, if an instrument needs to be deleted or added it's possible without too much diversion from the creative process. The idea that the sole function of MIDI is to imitate the traditional classical orchestra can be put to rest when we look at the creative options. Mixing unusual combinations of timbres is one of the new benefits of the virtual orchestra and there is a whole lot more to explore in this medium because of it's proven capacity to spawn new styles of orchestration and music. The key is to design an ensemble in which the instruments sound good together. As in so many aspects of artistic creativity, a particular element may be expressive and appropriate by itself, but in context it isn't contributing to the whole. If the ensemble is chosen with care and sensitivity we are off to a good start as each timbre will play an integrated part in the composition.

The Micro Level of Sequencing

It is impossible to discuss orchestration in the digital world without a brief discussion about sequencing. The digital orchestrator isn't just assigning musical parts to instruments, but also defining how those instruments will be triggered (played) on the final recording. Though traditional orchestration often involves precise instruction as to how notes and phrases are to be played, with MIDI the manner in which notes are sequenced and connected to one another is a matter of supreme importance. If care is not taken, phrases will sound mechanical (the death of expressiveness) and choppy, and no amount of brilliant orchestrating can obscure this problem.

The six essential parameters of concern to the virtual orchestrator involve each note:

pitch

duration

timbre

envelope (primarily amplitude attack and release)

velocity

time (location relative to the beat)

To sequence expressive phrases, satisfying legato, fast runs and other gestures, it is often that one or more of these parameters needs attention. Attack and release times, note length and velocity play a crucial role in the sequencing of a fine legato line, and sometimes a very small adjustment of one of the parameters does the trick. Even a loud tutti will not cover up these intimate connections between notes. In a fast passage for example, select every other note (or whatever group of notes represent the weak pulse to you) and lower their velocity by 20% or so. This helps shape the line by adding some variation, and also can be used to articulate where the accented notes are.

In a slow, legato passage, let's look at two half notes, we'll call them 1 and 2. Note 1's release time is one of the parameters that may need adjustment. The gate time, or actual length of note 1 is also tweaked, however with repeated notes if the note length exceeds the full value of the note, the second note won't sound. The goal is to get the attack of note 2 to become as neutral as possible, so that it sounds as though the moment the first note's decay is done the second note begins, but with no increase in amplitude. What is happening is that note 1's length is overlapping into the start of the note 2. Lengthening the 1st note by between 3-12% usually does the trick. It depends on the situation. By adjusting the velocity and attack of the 2nd note it is possible to sequence a smooth legato. Upon viewing a wave file of this connection, the wave file would appear with no jump in amplitude at the point where the 2nd note begins. As an adjunct to learning how to do this well, I highly recommend that the virtual orchestrator incorporates and works regularly with the human voice as an instrument in the mix, as there is much to be learned from the phrasing, dynamics and expressiveness of a fine and well-trained singer.

When sequencing brass, I prefer to use 3 individual trumpet patches to simulate a trumpet ensemble. The most obvious advantage is that you still have access to 3-part polyphony in the trumpets if so needed (if you use a brass ensemble in three-part writing you now have 9 instruments playing rather than 3!) In order to give those 3 trumpets some autonomy, I detune the left and right instruments (trumpets 2 & 3) by 20 cents or so, one higher and the other lower. I also move both trumpets 2 and 3 off the beat, one a bit advanced in time and one slightly late. Finally, trumpets 2 & 3 are panned hard left and hard right. This ensemble effect is varied by how much of these kindsof modulations you input.

Since a MIDI sequence is a performance of numerous instruments playing together, the virtual orchestrator is not only responsible for creating an effective orchestration but also must ensure that the sequence is rich with expression and detail. I cannot stress how important detailed sequencing is in regard to how the orchestration ultimately sounds. As in nearly all music production issues, when a problem is corrected earlier in the production process rather than later, the overall success of the final recording will be easier to achieve. Exceptions to this occur when flexibility is necessary. For example, not using EQ on the music until it is a wave file and non-destructive processing can be applied. This allows you to always go back to the midi file recorded with no EQ and the unprocessed wave files with the option of non-destructive processing. On the other hand, if you know the timpani is too boomy its best to deal with an isolated problem early as the balancing of the sound becomes more problematic if these individual cases of imbalance are not fixed in the orchestration and/or the mix. Why wait to EQ the entire mix and risk affecting an element you don't want changed? In this case EQ just that one instrument and save yourself trouble later on.

No matter how skillful your orchestration, if dynamics, tempi, or program changes are left static there is only so much that orchestration can accomplish in the MIDI ensemble. Masking an element that doesn't sound very good alone always hurts the music. The best approach is to isolate that element and make it work. If you want the whole to be greater than the sum of its parts I don't know of  any shortcut around this problem.

  

Textures

Mahler said the essence of orchestration is variety, variety, variety. I interpret this to mean that textural variation is of significant importance in orchestrated music. One moment music is homophonic, the next polyphonic. One moment only the winds are playing, in a choral-style texture, followed by a monophonic tutti or some other change in orchestration. Heterophony is commonly used to create melodic variation: One instrument (or several) play the primary melodic element while another outlines that same melodic line by playing only notes which accent the melodic curve. This can be done at the unison, at the octave; there are countless variations using this technique. A closely related technique is that of the join, drop-out, split and merge.

A join occurs when an instrument is playing a line and is joined by another timbre while in the middle of a phrase. A drop-out is the opposite; several instruments are playing a given part and one or more take rests, bringing variation to the texture. A split occurs when two instruments are playing the same part and suddenly one splits off and begins playing another part against the first instrument. A merge is the opposite, two timbres are playing two distinct parts and merge to give more weight to one of the parts.

Transparency is the principle by which all timbres that are used are contributing musically to the texture. If a timbre is not contributing, it should be removed. With a transparent texture, the listener hears the overall effect of the many timbres playing together, but one can also easily hear the individual parts that make up the orchestration.

The orchestrator strives to blend and balance sound, to create contrast and unity through the combinations of timbres. By blend we mean that when numerous timbres are sounding together, the overall effect is pleasing and no one instrument stands out unless the orchestrator wants it to. By balance we mean that the elements all sit well in their frequency and amplitude domains, that there is a conscious effort to allow which elements are primary in the texture, which are secondary, and which are playing a more subliminal role. This means also that balance is a function of structure as material that precedes and follows will likely determine how the composer decides what is primary, secondary or playing some other purpose in the texture. From a mastering standpoint, there must be a robust mid-range. If the middle frequencies are not there something will be missing. Every frequency you boost or cut affects other frequencies. If the bass is cut 2dB, the mid-range is now louder, relative to the low frequencies. Bob Katz discusses this in great detail in his book Mastering Audio, the best book I know of on the subject.. Balance is also about tweaking velocities and Control 7 (volume) so that the dynamics of each voice contribute to the effectiveness of the whole.

Orchestral Weight means that some elements are more heavily orchestrated than others. In homophonic music the melody may be orchestrated with numerous instruments in octaves, unisons or some other interval. Some elements may have a single instrument playing them. In a polyphonic texture the orchestral weight may be distributed more evenly among the individual melodic lines. As in the attempt to balance and blend textures, the orchestrator takes orchestral weight into account and orchestrates accordingly.

In the acoustic world, the role of the composer, conductor, mixing engineer and mastering engineer are often four different people. In the virtual orchestra world, orchestrating and mixing are sometimes indistinguishable, and mixing itself becomes a kind of conducting, albeit in virtual, or programmed time. Sonic balance is a concern throughout the process, and if great care is taken, the mastering engineer won't have a lot to do, although it always helps to consult with a mastering engineer from time to time. One's attempt to bring objectivity to their inner voice can only go so far. We sometimes lose awareness of the biased way we use our senses so having another set of ears can help verify what is working and help disclose any problems that may have been overlooked.

The Virtual Space: Panning and Reverberation

Many musicians like to pan the virtual orchestra by following the seating arrangement of the acoustic orchestra. But listening to music through two speakers is missing some of the sonic information that the concert hall provides so a technical response is required. The double basses in the orchestra are usually off to the right side of the ensemble. But with two speakers, the bass often sounds best in the center. If you're producing in surround this won't be of use, for now I am assuming stereo as the default. I prefer the 1st and 2nd violins panned hard left and hard right, violas soft left, cellos soft right and basses in the center. This gives a full stereo panorama of strings. When the 1st and 2nd violins are playing two distinct melodic lines, the stereo separation helps create the illusion of a larger space. An instrument sometimes employs a dynamic panning scheme, where the pan changes and fluctuates with the interplay of the pitches and rhythms, thereby using pan as dynamic rather than passive element in the mix. This is commonly done with percussion but can be done with any sound or voice.

With the winds, I tend to use reverb to create a softer, rounder sound, but in considering a smaller ensemble this may not work as well. To understand how to write better for the wind family listen to a piece such as Stravinsky's Octet for Wind Instruments. The virtual winds have been know to sound like an organ if the composer isn't paying close enough attention and/or the sample library is not of sufficient quality. A generous amount of reverb, fairly dark with a two second or more reverb time helps to soften the winds and blend them into the texture better.

Unlike in some acoustic situations where something may be recorded dry, I always monitor and record the virtual orchestra with reverb, and try to settle the reverb parameters early in the process. When I find a reverb I like I stick with it until I feel the need to change it. With singers every voice is different and may require a unique coloration of reverb. Though there is not one correct way to use reverb, reverberation is a critical element and even small adjustments in filtering, amplitude, or decay time can help produce a more expressive sound. 

Voice-leading:  the way to build balanced chords

Voicing the chords in the virtual orchestra should be done with utmost care. The study of harmony and counterpoint will greatly help the process of orchestration. But so will listening to textures in nature. Sitting by a river while a freight train passes by generates a profound counterpoint of rhythms and frequencies. Listen to sound in the real world and the natural world as often as you can. Pay attention and you'll be amazed at the way our brains process this information and project, imagine and hear music in what seems inherently unmusical.

It is in voicing that we choose the size and width of the chord on the vertical plane, but also on the horizontal as melodic motion. Orchestration is an interaction of harmony and melody, enlarged by timbre and texture. A balanced chord is one in which each note in the chord is at the right amplitude relative to the other notes. This is partly a matter of taste, to be sure, but a poorly voiced chord lacks integrated cohesiveness and balance and can upset the flow of the texture.

Prior to the theory of harmony, musicians did not think in terms of chord progressions. It wasn't until the 18th century that the French composer Rameau developed an accepted theory of chord progression and functional aspects of harmony. When we unconsciously assume that simultaneous melodic motion is nothing more than a chord progression, we have further codified the function of melody and have forgotten that harmony evolved from counterpoint, and that the linear aspect of chord motion is as vital as the chords themselves. This is one of the reasons I highly recommend dodecaphonic study: It greatly helps in developing a new understanding of voice-leading, one that urges resolution with the tonal traditions but that in itself offers a whole new set of options in your compositional tool kit and re-focuses attention on the contrapuntal aspects of composition, or at least one in which identifiable chords play a less important role in the form of the composition. Yet remaining on one chord for many measures, as in minimalism, can have the same effect: It can allow you to explore new contrapuntal conditions which changes the role harmonic progress has in your work.

Formal Functions of Orchestration

If we consider melody, harmony and harmonic progression, and rhythmic motifs as a way to assign structure to the musical impulse, certainly timbre and any possible vibratory movement within each timbre also may contribute to the structure. Orchestration, defined by this way of thinking, includes all uses of sound as a means of evoking texture. Whatever sounds we use, be they samples of acoustic instruments, complex synthesized textures, voice, live instruments, sounds occurring in nature and in everyday life, or sounds totally generated and processed via computer, there is an art and a craft to assembling these sounds in a meaningful and expressive way. Since all the sonic arts take place in time, we must always be cognizant of what came before and what came after the moment in the composition we are working on.

Unity and variety are two great concerns: Too much unity, or too much repetition without variation, and we run the risk of introducing predictability and boredom, too much variety or lack of structural cohesiveness and we admit chaos that may lack intelligent variation   and design. I strive to create compositions that have autonomy (everything seems to belong together) and inevitability (the music seems rightfully determined to resolve the way it does). This is not an easy undertaking as there appears to be inherently contradictory demands which require much thought, patience and musical insight to solve satisfactorily.

We are very fortunate to be living in a time where it is possible to access a liberal body of musical knowledge, literature and recordings. This makes possible the study music of other times and places, which can only advance our musical awareness.

Final Thoughts

Mastery of the basics is key to orchestration. All progress depends upon a clear understanding of the basics. The two basic ideas of inner listening and objectivity mean simply that as you listen to your work, listening becomes merged with imagination. This greatly quickens the creative response, but there a craft must develop, an objective understanding of your music and aesthetic.

Every project you complete is an outgrowth of what you have accomplished in an earlier work. The way to improve your orchestrations is by repetition, practice and analysis. It is no secret that the symphony orchestra's incredible richness, balance and beauty of tone is a great learning tool for any musician seeking to advance their knowledge of orchestration. No matter what style of music you write, it cannot hurt to study orchestral scores to see how master composers created their orchestrations. There is an ideal of beautiful sound and every generation of composers searches anew for this ideal.

In your own music, pay close attention to the harmonics in your orchestrations, listen to your sound deeply, and strive for clarity. Even if you don't want to sound anything remotely like a symphony orchestra, there is still much to learn by understanding how to infuse gesture, intention and expression in your work.

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