As well as the standard complement of equalisers, reverbs and delay-based effects, sequencers these days are bundled with an ever-increasing array of plug-ins designed to alter your sound in new and interesting ways. We explain how to use these effects in the forms in which they're bundled with the Big Five sequencers.
In our occasional series exploring the plug-ins bundled with MIDI + Audio sequencers, we've covered all the mainstream processors and effects, but that still leaves quite a lot of plug-ins unexplained. This month we're going to consider all the plug-ins that fall into a category I'll call Creative Modifiers. By this I mean processors that transform the entire signal in some dramatic way, rather than effects which work by adding a delayed, reverbed or pitch-modulated signal to the original. That's not to say that some Creative Modifiers don't give you the opportunity to mix in some of the dry signal, but in the main this would be done within the plug-in itself rather than via a send/return loop. In terms of signal path, Creative Modifiers are therefore treated in the same way as processors like compressors or gates, which means using them in insert points rather than aux send/return loops. A prime example of a Creative Modifier is distortion, but the term also encompasses pitch-shifters, various kinds of enhancers, and amplitude modulation devices. All right — as we thought up the term, it can cover whatever we want it to! It could also cover dramatic filters used for effect, but since there are so many of these we'll be covering them separately in another article.
Distortion Plug-ins
At one time, distortion simply meant overdriving an analogue circuit to create hard or soft clipping, but in the digital domain, there are more mechanisms that can be brought to bear. Clipping distortion is the easiest to create: you simply increase the level of the signal so that it reaches the maximum level (digital full scale or DFS) for a significant amount of the time, at which point the waveform gets its top and bottom flattened. This usually sounds pretty gritty and nasty unless some serious filtering is applied afterwards. When a plug-in is called Distortion or Overdrive, it normally means that it 'rounds off' the tops of the waveforms by means of a non-linear characteristic intended to emulate the way analogue circuitry tends to behave when overdriven. Though much smoother-sounding than clipping, this can still sound somewhat ugly when used heavily unless top cut filtering is applied, and many plug-ins include some form of filtering for this purpose. Overdrive and distortion effects are similar in character to the distortion that occurs within a guitar amplifier, though in the case of the guitar amplifier, the necessary top cut filtering is provided by the speaker, which is designed to have a limited high-end response.
Another type of distortion made possible by digital processing is simply to 'miss out' some of the bits so that a 16-bit resolution signal can be reduced to 8 or even 4-bit resolution. This introduces a lot of ugly quantisation distortion and quantisation noise, and is reminiscent of the sounds that used to accompany very early video games. By selectively turning off bits, the distortion pattern can be made even more complex so that a sine wave input produces a complex-shaped output — something you can see graphically represented when you try the different distortion modes in Logic's Bit Crusher. It's also possible to reduce the sample rate of a signal (usually by dividing the sample rate by 2, 4 or 8) to produce nasty aliasing effects, should these be in any way desirable!
Loud Bit, Quiet Bit
Amplitude modulation, in essence, means turning the volume up and down in a regular pattern. If you do this fast enough, you actually change the shape of the waveform and hence the tonal content of the sound, which is why you will sometimes find synths that offer amplitude modulation as a feature. If your modulation source is a low-frequency oscillator, however, you will get a tremolo effect similar to those found in some guitar amplifiers. More sophisticated tremolo plug-ins often offer a variety of modulation wave shapes and combine amplitude modulation with auto-panning to create movement in the stereo field.
Shifting Pitches
Pitch-shifting is sometimes thought of just as a means of rescuing out-of-tune singers, but it can also be used as a creative effect, as all pitch-shifting algorithms tend to introduce side-effects into the sound. The reason is that all simple pitch-shifters work by slicing the audio into very short sections and, when increasing the pitch, these short sections are looped and then spliced back together after being sped up. When the pitch is being dropped there's no need to loop, but the slowed-down sections still need to be cross-faded into each other as they're now longer than they were originally. Inevitably there's an audible modulation, the rate of which corresponds to the length of these short audio sections (which are usually only a few milliseconds long) and this has the effect of making the shifted sound appear out of tune. When small amounts of shift are being applied for detuning purposes, this modulation may be negligible, but when shifts of multiple semitones are used, it becomes glaringly obvious. I don't tend to use pitch-shifting as an effect myself, because I don't find the side-effects at all musical, but others do, and the pitch-shifting algorithms in Akai samplers, for instance, have been widely used (or abused!) in jungle and drum & bass productions.
Another pitch-related effect is the sub-octave generator, which works by taking a narrow section of the existing bass end and then halving its frequency using a 'flip-flop' similar to those used for creating sub-octaves in early electric organs. The crudest octave dividers use the flip-flop's square wave output (usually heavily filtered) as the sub-bass signal, but better designs use this square wave to control a phase switcher that works on the original piece of filtered low-end audio. What comes out is best explained in terms of a sine wave. A sine wave has alternative positive and negative-going cycles, but after being treated via a phase inverter triggered from the original sine wave via a flip-flop, what you get out are two consecutive positive peaks followed by two consecutive negative peaks. This has a sub-octave component and the signal level follows the amplitude of the original sound. Heard without filtering, it is pretty distorted and nasty, but by filtering out all the high frequencies and then summing the synthesized sub-bass signal back in with the dry signal, the impression of added deep bass can be quite convincing. The sound quality also improves if there are two or more divider circuits operating at the same time, each one fed from a slightly different region of the original signal's bass end. The widely used Dbx Boom Box, which works on this principle, operates on four frequency bands at once.
Enhancers
At the other end of the frequency spectrum, some kinds of enhancer add high-frequency content to a signal to create artificial brightness and 'air'. The most popular type of enhancer is based on a principle discovered by Aphex, where artificially generated harmonics are added back into a signal to create high frequencies that were never present in the original signal. This can be done quite simply by using a high-pass filter to feed a side-chain that uses a combination of compression and distortion to generate the new high harmonics. A high-pass filter is needed to restrict the input to the side-chain, because if low frequencies are allowed into the distortion generator, the added harmonics fall in the audio mid-range where they are perceived as distortion. By limiting the added harmonics to above 5kHz or so, they are perceived as natural providing they are not added at too high a level.
While the previously described enhancer works on the frequency content of the signal, other types work on the stereo width. A simple system that inverts the phase of the left channel and then feeds some of this into the right channel, and vice versa, can increase the sense of stereo width without compromising mono compatibility as the added out-of-phase components disappear when the two channels are summed to mono. It is also possible to process a mono signal to give it a sense of stereo spread (or to widen an existing stereo signal) by using filters to place peaks and troughs in one channel and the exact inverse in the other channel. Often this is achieved using comb filters as these are easy to design digitally and can have lots of frequency bands. Because the processing in the left channel is the exact opposite of that in the right channel, the signal sounds unchanged when summed to mono, but when the two artificially created (filtered) outputs are panned hard left and right, the signal appears very wide. This type of process doesn't provide independent positional information for the different components in a processed mono mix but it can produce a general impression of space and width. The process is particularly effective on synth sounds that have a high harmonic content.
Creative Modifiers In MOTU's Digital Performer
The simplest of DP's Creative Modifiers is Quan Jr, which is really just the bit-depth-reduction section of the Masterworks Limiter plug-in. As well as providing dithering and noise shaping options for sensible bit-depth reduction, Quan Jr can do those trendy 'digital grunge' effects as well. Simply lower the Bits value to something below 16 — and get ready for some real dirt with values or eight or lower. Remember to turn off dither to keep the plug-in 'quiet', and exercise caution when reducing bit depth to 3 or less, as then even the quietest input signals are quantised to high amplitudes.
Preamp 1 has a number of different modules, including a single-band compressor which was discussed back in March's Sequencer Dynamics Masterclass (www.soundonsound.com/sos/mar03/articles/sequencerdynamics.asp). It's the Pre-EQ and Coloration sections, though, that do most to radically alter a signal's harmonic structure. Pre-EQ by itself is nothing special — just two parametric bands plus a simple low-shelf or high-pass type — but its interaction with the Coloration controls makes it interesting. Basically, there are two Coloration modes: Subtle, for valve warmth, and Drastic for overt distortion. The exact functions of the Drive, Timbre and Push buttons are a little mysterious — Drive seems to be an 'overdrive amount' control, introducing distortion, whilst Timbre alters the quality of the overdrive, from restrained to chaotic. However, for anything much to happen at all, you also need to turn up the Push control. Coloration can additionally be made to behave dynamically, coming into play when the input signal exceeds the threshold level of the compressor section, whether the compressor is enabled or not.
DP's Ring Modulator is a classic implementation of this kind of effect, and has a funky animated display to boot! The track on which you place the plug-in is used as one of the input sources (the carrier), and there are several options for the sourcing of the other (the modulator). One is to use the plug's built-in oscillator, which has a wide frequency range and selectable waveforms. You can even 'play' this oscillator via MIDI — in DP4, any active Ring Modulator should automatically show up in all MIDI output popups. For more on configuring this in earlier versions see Performer Notes from way back in September 2001 (www.soundonsound.com/sos/sep01/articles/performnotes0901.asp). Other modulation sources include the carrier signal itself (Effect Input), and any other audio routed into the plug-in via one of DP's internal busses — all this can be configured using the Modulation Source pop-up menu. Other controls include a gain for the modulation source, a low-pass filter for toning down the inevitable metallic harshness, and a wet/dry mix control. Finally, Sonic Modulator could be DP's least well-understood plug-in. Originally intended as a Leslie speaker simulator (hence the two-way crossover and Doppler-effect-capable pitch-shifters), Sonic Modulator can do all kinds of freaky things, albeit only on mono channels. See October 2002's Performer Notes (www.soundonsound.com/sos/oct02/articles/performnotes1002.asp) for a full explanation of this great plug-in.
Robin Bigwood
Logic's Creative Plug-ins
I can't promise to have covered absolutely every Logic plug-in, though I hope this series has cast light on the most important ones. The simplest Logic distortion-type plug-in is Clip Distortion, which like the other distortion devices in the series, features a visual display intended to show how much the signal is being processed. A variable Drive slider determines how heavily the input is clipped, but the strength of this particular plug-in comes from a comprehensive set of filtering tools that allow the signal to be low-pass filtered prior to clipping and again after clipping using the Tone and Filter sliders. The symmetry of the clipping process can also be changed using the Symmetry slider. A Mix control allows the dry and distorted signals to be combined if required, after which the signal passes through yet another low-pass filter (just 6dB/octave this time) controlled by the Sum Filter knob, before encountering a tunable shelving filter with a massive ±30dB range. The idea of all this filtering is to allow the user to control the severity of the added harmonics.
Overdrive is a little simpler, having only Drive, Output Level and Tone controls. This attempts to emulate the overdrive characteristics of an FET (Field Effect Transistor), which isn't dissimilar to the way a tube 'soft limits'. The Tone control cuts the higher harmonics to take the rough edge out of the sound, though it isn't as sophisticated as using a speaker simulator. Distortion offers a similar set of controls but the distortion characteristics are modelled on those of a standard bipolar transistor rather than an FET.
While the previous two plug-ins try to capture something of an 'analogue' feel, Bit Crusher has no such pretensions. You can reduce the bit rate and the sample rate to create horrendous quantisation distortion and aliasing, while Drive just piles on more distortion. Clip determines at what level clipping should occur, though the Mode buttons allow a choice of outcomes when the signal reaches clipping level as can be clearly seen in the display where you may notice the peak of the waveform 'folding back' on itself rather than being clipped flat. You have to listen to these sounds because they're hard to describe and, to be honest, even harder to like unless you're into hard industrial dance with a nasty edge! Nevertheless, I have used this plug-in with some success to liven up a soggy snare drum recording.
Phase Distortion is quite different again, as it uses a modulated delay line as its engine, where the modulation source is a resonant low-pass-filtered version of the input signal. In effect, the input modulates its own wave shape. The maximum delay time of the modulated delay is set using the Max Modulation control, while Intensity regulates the modulation depth. Mix allows the original signal to be blended in with the distorted signal. Used with care, this plug-in works particularly well on monophonic synth bass lines to warm, fatten and roughen. In combination with the Emagic ESM synth, you can create some very powerful dance bass sounds. Think of it as an easy way to add phase distortion synthesis in the style of the Casio CZ101 to your own sounds — but be warned that it sounds pretty nasty on polyphonic sounds.
Logic's Exciter is a fairly straightforward implementation of the 'added harmonics' enhancement process, where the two Colour settings correspond to different distortion mechanisms and hence different spectra of added harmonics. The Frequency control sets the low limit of what is fed into the side-chain, while Harmonics controls how much harmonically enriched signal is added into the dry signal. The Input button may be used to kill the dry signal either to check on what's being added or to enable Exciter to be used in a send/return loop. Though enhancers are not normally used in send/return loops, they can be used this way providing there is no delay between the dry and the enhanced signals. Activating plug-in delay compensation ensures timing accuracy for effects used in channel insert points but it doesn't work for Logic's busses (which is where you normally park your send/return effects), so you may have to insert a Sample Delay plug-in into the dry signal path and do the compensation manually if you wish to experiment with this mode. Personally I always stick to using this plug-in via individual channel insert points unless processing a whole mix.
Stereo Spread is a different type of enhancement intended to increase the apparent stereo width of an existing stereo signal or to simulate stereo from a mono signal. It works on the principle of cutting and boosting frequency bands in one channel and doing the exact opposite in the other as described earlier, though to prevent the bass end from suffering, the processing affects mainly the mid and high frequencies. There are controls to adjust the upper and lower frequencies affected while the Order knob dictates how many frequency bands the signal is split into. It's safer not to enhance bass frequencies too much as it can sound odd, and can also make mixes impossible to cut onto vinyl.
Sub Bass is almost like an enhancer in reverse, insomuch as it adds low-frequency components below those that existed in the original signal. In this implementation of the process, the added subharmonic is sinusoidal and two separate sub-bass components can be derived from two separate sections of the audio spectrum (typically 80Hz to 200Hz) in order to produce a smoother result. The system works with any material — monophonic or polyphonic parts, or entire mixes — and the bandwidth of the material being used as a source for subharmonic generation is user-adjustable. Though it is possible to set up different division ratios, it is usually best to stick to a setting of 2 to produce single-octave subdivisions. Each of the two 'voices' has Ratio, Centre and Bandwidth controls and the amount each contributes may be adjusted using a Mix control. Further controls regulate the dry and sub components. In typical applications, the centre frequency for the higher band should be set at roughly 1.5 times that of the lower band for the smoothest results. Used in small doses, Sub Bass is effective for adding weight to weak drum tracks or bass instruments, but used to excess it can shake loudspeakers to pieces, so use it carefully and sparingly.
Tremolo is quite straightforward, but goes a lot further than the tremolo you find in your guitar amp as the modulation waveshape is continually adjustable both in width (Symmetry) and smoothness, so it can be a square wave, a pulse wave or a wave with a smooth attack. Mono or stereo signals can be processed and the two outputs of the plug-in can either work together to provide a conventional amplitude modulation tremolo effect, or they can be adjusted in phase so that they overlap or alternate, producing a panning tremolo effect. The depth of modulation is controlled via a single slider, but most exciting is the Rate control, which at one end of its travel sets the LFO speed in the usual way, but at the other offers a number of tempo-locked subdivisions. Set to modulate at 32 cycles to the bar, this produces a wonderful rhythmic gating effect that can be used to lock any pad or sustained part into the groove of a track. This is one plug-in you shouldn't overlook.
Creative Modifiers In Digidesign's Pro Tools
  However, Digirack also includes a selection of Audiosuite off-line processing plug-ins, and some of these certainly allow you to modify your audio creatively. Although you can't use them in real time, they do include a preview function, and Pro Tools multi-level Undo means that you can safely mess around with them to get the effect you're after. Audiosuite plug-ins act on the currently selected section of audio in the Edit window. Reverse does exactly what the name suggests — take a section of audio and turn it back to front. Reversed cymbal hits or guitar chords are very useful for creating tension to mark the end of a dropped-out section in your song, for example. Time Compression/Expansion and Pitch-shift are also self-explanatory. Both offer an Accuracy slider that travels between Sound at one extreme and Rhythm at the other, the idea being that you can choose the least bad compromise between audible side-effects and tempo drift. In practice I find that this doesn't always make very much difference, and that even with the slider all the way to the right, long selections end up out of time when pitch-shifted. Unlike Paul White (see main text) I use both of these effects all the time in a musical context — my favourite application is pitch-shifting a DI'd guitar part up or down by an octave before feeding it through an amp simulator. Sam Inglis |
Creative Plug-ins In Cubase VST & SX
Cubase also has a tremolo, again combined with a stereo/mono button so you can produce auto-pan effects. With the Sync button active, one unusual effect is to choose the square wave option with a slow speed setting, and use it to process a drum loop — you can gate specific beats, and with the stereo button active these will leap from speaker to speaker, perfectly locked to your song.
On the distortion side, the oldest and most unsubtle contribution in the Cubase stable comes from Fuzzbox — a simulation of a transistor stompbox. This can run the signal into coarse clipping, but as long as you keep its Boost control to 25dB or less it's actually quite useful for thickening a sound without obvious distortion, while Clipback inverts the signal above clipping level to produce higher levels of second harmonics. Try 15dB Boost and vary the Clipback on a drum loop to taste.
Distortion is more comprehensive, providing a selection of five distortion algorithms that each generate a series of odd harmonics: Soft, Crunchy, Dirty, Wracky and Evil. Three Shapes determine the I/O transfer characteristic, while the Drive control determines the amount of distortion, and the Contour control is described as a high cut filter, although it also seems to cut low frequencies at settings below 50 percent. Distortion is capable of a wide range of effects from a soft crunch up to cone-bending overload, but I find the Soft, Crunchy, and Dirty algorithms (with Drive settings of 50 percent or less) more practical with most sounds than the Wracky and Evil algorithms, which tend to mangle things beyond recognition.
Datube is altogether more well mannered, offering valve emulation that (unusually) provides even as well as odd harmonics, as well as a Balance control to mix in the untreated signal for even more subtle results. With an input signal peaking at 0dBFS, its Drive control lets you dial in just a few percent of distortion to add a little warmth when it's down in the 10 to 20 percent region, rising to 10 percent distortion at around 40 percent Drive, while at 100 percent the distortion is only around 6dB down on the signal level. This is an enhancer plug-in that you can safely use on a complete mix as well as individual tracks.
Overdrive is a guitar amp emulator, with optional speaker simulation that rolls off the top end, and a three-band EQ providing ±15dB gain variation. It falls somewhere between Datube and Distortion in severity, its six amp styles providing different basic algorithms that once again generate various amounts of both odd and even harmonics — the graphic window provides a rough but useful guide to the number and amount of generated harmonics. I find the suggested presets rather heavy-handed, and it's quite possible to generate a lot of useful amp models with Drive settings of 30 percent or less, where the various algorithms still add plenty of character without sounding shredded.
Quadrafuzz is a clever concept by SOS contributor Craig Anderton. The audio is split into four user-defined frequency bands, and then each is distorted individually and filtered once again before being finally mixed together. There are five distortion types, and the results are incredibly versatile, as demonstrated by the 32 presets — you can even use it to isolate and distort one drum in a groove with care!
Bitcrusher from FXpansion is very similar to its namesake in Logic Audio, providing four operating modes with subtly different amounts of grit and noise, plus a Sample Divider that further decimates the output — at its lowest setting all the signal gets through unscathed, while increasing it sounds rather like detuning a radio station, and at high settings the output signal can be almost unrecognisable. You can add some grit with Depth settings ranging from 10 to seven bits, while lower settings sound more like blown loudspeakers and faulty amplifiers (should you desire them).
Grungelizer also adds noise and grunge to your sounds, but this time in a chronological manner, by emulating the historical limitations of audio devices. These encompass vinyl crackle, tape and amplifier hiss, large amounts of second-harmonic distortion to mimic stylus geometry, EQ limitations, and AC hum at either 50Hz (UK) or 60Hz (US) frequencies, plus control of the overall level of all five effects via a Timeline control labelled from 1900 to the present day. Although this has obvious uses for anyone working in period drama, the EQ provides a useful combination of LF roll-off and mid-range peaking that might prove useful elsewhere (perhaps to simulate yet more guitar amps), while at lower settings the Distort control is very useful as a second-harmonic enhancer — just turn all the knobs right down except Distort to add extra attack and thickness to drum sounds.
Sonar's Creative Modifiers: the Amp Sim and Tape Sim plug-ins.MDA's Sub Bass is altogether more versatile than its counterpart in Logic Audio (and if you're not a Cubase user, is available for free download from www.mda-vst.com along with other MDA plug-ins) with three completely different modes to add new low-frequency information. In all cases the easiest way to set up the controls is to first turn the Dry level down to zero so you can hear the generated bass component by itself. Once you've got something suitable, turn up the Dry level again, and then add some FX level to taste.
Boost mode simply warms up the bottom end with EQ, with the Tune control adjusting the turnover frequency, Drive adding some crunch at higher settings, and Tone adjusting the high-end response, while Threshold lets you set the trigger level. Trigger mode generates a drum synth sound triggered each time the input signal rises above the Threshold setting, with Tune now setting the oscillator frequency, Drive altering its waveform, and Tone its decay time, although I've found this mode prone to mistriggering, however carefully you set the Threshold control.
Divide mode is my favourite, generating a pitch-tracking signal an octave below the input signal, with the Drive control now affecting the waveform of the sub-octave component. This can generate some seriously low signals that may be felt (or on nearfield speakers just seen) rather than heard, so watch your speaker cones carefully for potentially dangerous subsonic movement. To enhance a bass drum, start with Tune and Tone settings of 50, Drive at zero, and then start the Threshold control at 0dB and move it down until the effect only cuts in where desired, to avoid unwanted continuous rumbling sounds.
Creative Plug-ins In Sonar
I've heard it said by several enthusiastic Sonar users that one of the reasons that its price is less than that of many other MIDI + Audio sequencers is that you don't have to pay for a huge bundle of plug-in effects that you may or may not want. This is certainly true when it comes to the more creative effects, as there are just two — Amp Sim and Tape Sim — which together comprise Cakewalk's Audio FX2 pack.
Amp Sim models the desirable effects of tube guitar amplifiers, along with various speaker cabinets and a virtual mic position. There are eight amp models covering American and British, tube, solid-state, clean to distorted, along with a No Amp option that simulates a DI box. All the amps have Drive, an EQ section comprising Bass, Middle, Treble, and Presence, a Bright switch, and output Volume, plus a Tremolo section with rate, depth, and bias controls. Together these options provide a huge range of sounds, and they then pass into a selection of speaker enclosures (1x12, 2x12, 4x10, or 4x12), with a choice of open or closed back, along with a Direct Out (no speaker) option, and on or off-axis mic position. Of course, guitars are ideal candidates for Amp Sim, but I've also found it very useful for basses and drum loops.
Tape Sim simulates the effects of recording your audio on an analogue tape deck, including overload compression, saturation, and even tape hiss! It generates the complete range of odd harmonics (3, 5, 7, 9 and so on), at a level determined by the Rec Level control, and relative balance by the Warmth control. It also has a variety of other tape effects on offer, such as Tape Speed and EQ Curve to simulate the high end response of analogue recorders running at between 7.5 and 30 inches per second, and NAB bass boost. It works well with drums and loops, but I've always found it too heavy-handed to add life to an entire mix.