There are many reasons that electronic music sounds different from music produced by acoustic ensembles. A performance on most acoustic instruments involves countless variations in properties such as volume, timbre, rhythm, articulation, and pitch.

In contrast, musicians performing on electronic keyboards can vary timbre and volume by using sounds that respond to MIDI Velocity and other controllers. They can create variations in rhythm and articulation by their degree of dexterity. But subtle pitch variations of less than a semitone are generally missing in most electronic-keyboard performances. Fortunately, by adjusting some basic pitch controls available on most synthesizers, you can enhance the music you and your students produce.

One of the mixed blessings of early analog synthesizers was their tuning instability. The 950 Keyboard Controller on the modular Moog synthesizer I used in college often had to be tuned or scaled from the lowest note to the highest so that it played in tune. The legendary Moog 901B oscillators also were famous for their instability. By the time I had tuned the sixth oscillator, the first oscillator usually had drifted a little sharp or flat.

FIG. 1: You can obtain a thickening effect by slightly detuning one or more tracks relative to each other. Here, a note is being sustained in Cakewalk’s Sonar 4 sequencer, while a small amount of Pitch Bend (called “Wheel” in Sonar) shifts the note up and down by a fractional amount.

The oscillators in many analog synths were greatly influenced by temperature changes, and during winter sonic chaos resulted whenever I opened the window in the studio for some fresh air. Adding to the instability from known causes were mysterious electrical anomalies that sometimes occurred in analog synths. For instance, crosstalk between circuit-board traces in some models could cause unpredictable behavior.

The combination of unstable oscillators, keyboard controllers — and, in some cases, performers — produced some wild sounds. Whether that was good or bad depended on your creative philosophy and the music you were trying to produce.

Today's instruments are extremely stable. This is desirable when playing samples of fixed-pitch instruments such as piano, celeste, and most pipe organs. On many sounds, however, a bit of subtle pitch variation can be a good thing, adding thickness, motion, and (when emulating certain acoustic instruments) realism.

You can use several techniques to inject some pitch variation in your ensemble performances and sequencer tracks. While none of the techniques presented here begin to approximate the complexity of pitch variation on most acoustic instruments, they can be used judiciously to improve the sound of your music.

Tuning different keyboards slightly sharp or flat is the easiest way to create a thicker texture. If your class is performing as an ensemble, tune some keyboards sharp by several cents (hundredths of a semitone) and others slightly flat. Beat frequencies will dominate only if all students play the same notes at the same time using the same sound.

There are two ways to detune most synths: either go into Global mode and adjust the Master Tuning, which will affect all of the sounds, or detune specific sounds or programs individually.

You can create a similar detuning effect in sequencing programs by adding small pitch offsets to a few tracks (see Fig. 1). This can be done in any sequencer by inserting a Pitch Bend message at the start of the desired track. There is no one correct value; try adding a small amount of positive or negative Pitch Bend, and listen to the track.

Modulate the oscillators' pitch. Another option is to set up a low-frequency oscillator (LFO) to modulate the pitch of the synth's audio oscillators by a very small amount. Depending on the LFO waveforms that your synth can produce, the variation might be regular (say, using a sine wave as a modulation source) or irregular (using a sampled, complex waveform as a source). By varying the modulation depth with an envelope generator or a real-time controller (such as a footpedal or slider), you can adjust the amount of pitch variation. For the subtle variations we're after here, use only a small amount.

Many synthesizers include a feature that randomly detunes each note played. The degree of randomness is usually adjustable, from none to untempered intervals more than an octave away from the original pitch. Some synthesizers may have only one global setting for random detuning; others allow you to add the effect on individual programs. A small amount of random detuning can help to thicken up ensemble sounds such as strings, brass, and voices.

Certain microprocessor-based instruments make it easy to create and store different keyboard tunings or temperaments. Many software synthesizers (such as Native Instruments' Reaktor) allow this, as well. While alternate temperaments will not work with most contemporary Western music, they can sometimes create a breathtaking effect with early music and some electronic-music genres.

Another simple way to add pitch instability to your music is to use acoustic musicians. All it takes is one voice, one violin, or even one guitar to introduce subtle but important pitch variations.

I know some readers must be thinking, “Are my students really going to hear these differences?” In many cases the answer is “Yes,” but it depends on each student's ears. I have absolute pitch and am hypersensitive to pitch variations. I vividly recall the first time I selected just intonation on a synthesizer and played a Bach prelude; the new pitch colors made me feel as though my head were going to explode a la Dr. Belloq at the end of Raiders of the Lost Ark. (It's a mixed blessing, though. Musicians with absolute pitch find it almost impossible to use keyboard transposers.)

Your students certainly won't raise their hands and complain that the +9 cents detune on track 7 is bothering them, but most will hear a “thicker” sound in much the same way that they hear a “bigger” sound when reverberation is added.

Most listeners can hear and respond to the outrageous whammy-bar nosedives made famous by Edward Van Halen; fewer can appreciate the subtle pitch slides or intentional note flattening or sharpening of a jazz singer or blues guitarist. Adding the pitch variations I've described does not involve performance skills, so why not aim high and make your music sound its best?

Don Muro's CD Reflections can be found at www.donmuro.com. His book, The Church Musician's Guide to Music Technology, can be found at www.giamusic.com. His music-technology lesson plans for the Expressions Music Curriculum are available from Warner Bros. at www.music-expressions.com.