Flanging, chorusing, phasers, tremolo, and auto-panning are the most common types of modulation effects in modern synths and digital audio workstation software.
Since each of these effects has its own flavor, this tutorial will cover the specifics of what to use and when to use it.
For example, flangers are great for adding animation to percussion and sweeps, but can be problematic when used on bass.
Let’s find out why.
Since all modulation effects rely on LFOs to animate their processes, we recommend reviewing the Guide To Synthesis LFO tutorial to get the most from this lesson.
That said, here are a few parameters that are common to the majority of modulation effects.
Rate/Speed. Rate – or speed – is the parameter that determines how fast the modulation effect cycles. If the effect can be synced to tempo, this parameter locks the cycling to a specific note value (such as quarter-notes or eighth-notes), which then correlates with the BPM.
Depth/Amount. This parameter is self-explanatory. It determines the overall amount of LFO modulation in a given effect.
Waveform. Many, but not all, modern modulation effects offer an array of common LFO waveforms. If your modulation effects do not include a waveform selection option, the default waveform will almost always be a triangle or sine wave.
Mix. As with delays and other effects, the mix parameter determines the balance between the wet (processed) and dry (unprocessed) signals.
Envelope parameters. In addition to an LFO, some modulation effects (like those in Ableton Live) include envelope parameters. Working in conjunction with an “envelope amount” knob, these parameters allow the effect to be modulated by the audio signal’s loudness, introducing a dynamic element to the effect – this can be quite useful for rhythmic parts.
As mentioned in the our delay tutorial, flanging –and chorus, discussed below –is based on the principle of taking a short delayed signal and modulating the delay time with an LFO as the signal is being processed.
Because of the very short delay times involved in flanging, the phase artifacts created by this technique create a metallic, ripping effect that some have compared a jet taking off – one of the reasons flangers sound so great on whooshes and sweeps.
Delay time. The delay time controls the overall character of the flanger’s sound, with shorter delay times creating classic higher-pitched jet flanging and longer times generating ringing metallic effects.
Feedback. By feeding the wet signal back to the input of the flanger, the intensity of the effect is increased, producing more pronounced pitches. Too much feedback can sometimes introduce extremely loud resonances, so proceed with caution.
High-pass filter. Many flangers include a high-pass filter option which limits the flanging effect to just the upper frequencies, allowing the fundamental and lower frequencies to pass unaffected – very handy for bass and midrange pad sounds.
Flangers sound best when blended with the original dry signal to enhance the phase aspects of the effect.
By reducing the modulation amount to zero and increasing the feedback to 75-90%, a flanger can be used to generate a single, tunable, resonant frequency – much like Live’s Resonator device.
That resonant effect can be tuned using simple math: divide 1000 by the number of milliseconds to get the frequency in Hertz: 1 ms = 1000 Hz (or 1kHz), 2 ms = 500 Hz, 4 ms = 250 Hz, and so on.
Flangers can impart a subtle (or drastic) motion to high-frequency percussion sounds like hi-hats, shakers, tambourines, and such.
While flangers can be used effectively on bass sounds, when doing so it is extremely important to set the high-pass frequency to at least 500 Hz, often higher.
Since the process of flanging introduces phase artifacts into the combined wet/dry signals, it can frequently cause the bass frequencies to cancel, making the low-end of your mix fluctuate unpleasantly in volume.
By placing a high-pass filter at the input stage of a flanger, we can limit the range of the effect to the upper frequencies, leaving our precious lows intact.
Chorusing uses longer delay times than flanging, but the principle is essentially the same – an LFO modulating the time of one or more delays.
Because of the increased delay times, the modulation results in a distinct pitch wobble, almost a vibrato, that is then blended with the dry signal to simulate the effect of multiple detuned voices – hence its name.
You can actually hear what’s going on inside a chorus by setting the mix to completely wet, then increasing the delay time and modulation amount.
Done correctly, the result should be a seasick, wavering pitch.
Some choruses include multiple delays that are modulated one or more LFOs – this results in a thicker effect that is sometimes referred to as “ensemble.”
Delay time. The delay time controls the overall character of the chorus sound, with shorter delay times creating more flanger-like effects and longer times generating vibrato.
Feedback. By feeding the wet signal back to the input of the chorus, the signal becomes more metallic and flanger-like. As such, feedback should be used judiciously if you want a more natural sound.
High-pass filter. Like the flanger, the high-pass filter limits the effect to only the frequencies above the high-pass cutoff frequency, allowing the fundamental and lower frequencies to pass unaffected, which reduces mix clutter and unwanted phase artifacts.
No matter what signal you’re processing, a touch of high-pass filtering will help enhance the chorus effect and keep the track sounding tighter.
A quick shortcut to the classic trance lead sound consists of taking a simple sawtooth-based synth patch, opening the low-pass filter to max, then applying one or more choruses (each with different settings) to the result.
Start by keeping the chorus mix amounts to 50/50 wet-dry so the sound doesn’t get too liquid-like.
On the other hand, if watery is what you’re after, take a muted sound like a triangle wave synth sound, extend the sound’s amplifier envelope release so it trails off slightly, then slap a few really wet choruses on it.
Be careful when using chorusing on vocals, a little goes a long way, unless you want a really retro Pink Floyd effect (which of course, could be totally cool in the proper context).
While the whooshing sound of a phaser bears a passing resemblance to the sound of a flanger, each effect is produced using its own unique process.
Phasers work by applying an array of all-pass filters to the audio signal.
An all-pass filter passes the audio’s entire frequency range, but alters the phase of various frequencies – or broader ranges of frequencies – as the signal is processed.
Since the human ear generally ignores the phase of the audio unless it is in relationship to a second audio signal, the phasing effect includes a blend of both the filtered and dry audio signal.
The complexity of the phase effect is determined by the number of stages, which correlates to the total number of all-pass filters in the array.
Number of stages. Sometimes referred to as number of “poles,” this parameter governs the overall spectral intensity of the effect. That is, lower amounts create subtle animation, while larger amounts introduce the “whooshing” sound that producers associate with this effect.
Frequency. Sometimes referred to as “center frequency,” this parameter varies the phaser’s response toward the lows, mids or highs.
Feedback. As with flangers, the feedback parameter routes the processed signal back into the effect’s input. Small amounts enhance the frequency sweeps, larger amounts create a ringing pitch that follows the sweep – or remains static if you reduce the LFO amount to zero.
Other parameters. Ableton’s phaser also includes two parameters: earth/space and color. Earth/space is an Ableton-specific mode switch that toggles between classic (earth) and metallic (space). The color parameter is subtler and simply modifies the character further.
Phasers have the most pronounced effect on sounds that have some high-frequency content, like breathy vocals, bright sustaining pads, and whooshes.
This processor also sounds great inserted after long delays or reverbs, adding animation to the sound as it trails off.
As with flangers, using a phaser on a bass sound can be a tricky affair that requires using a crossover or high-pass filter to limit its effect to only the upper frequencies of the audio signal.
The difference between an autopanner and a tremolo effect is that the former is stereo, while the latter is mono.
Autopanners allow you to apply an LFO to the position of a sound in the stereo field, making it move cyclically from left to right and back and so on.
Tremolos modulate the volume of a signal, introducing a quiver or throb to the loudness.
Phase. Determines the phase relationship between the left and right channels – in Ableton, the maximum and minimum amounts sum the signal to mono, creating the tremolo effect.
Offset. Determines the starting point in the LFO wave’s cycle.
Shape. Found on Ableton’s implementatation, the shape knob makes the overall waveshape more square-like for harder, gated effects.
On most DAWs, this effect can either run freely or be synchronized to tempo and each mode yields different results
Slow-to-medium unsynced autopanning can add a slightly more organic nature to pads and leads when used with restraint, though syncing to tempo can obviously help reinforce a track’s groove.
Extreme amounts of autopanning generally sound best when synced to tempo.
To quickly get a rhythmic, gated effect from Ableton’s autopanner, turn the phase to zero (to create tremolo), turn the shape knob to maximum (to create a square wave), sync to tempo, then adjust the amount and rate to taste.
Pictured at right, this technique is a lot faster than using clip envelopes, provided you want a consistent rhythm like eighth or sixteenth notes.
Another tremolo-based shortcut is to use a tempo-synced, monophonic autopan to simulate sidechain compression on bass or pads in a four-on-the-floor track (doesn’t work quite as well with breaks, due to the consistent nature of LFOs)
Here, the trick is to set the tremolo to quarter-notes, then adjust the offset parameter so the sound bobs in volume, alternating with the kick.
Until next time, keep those comments and suggestions coming!