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Using Your Plug-in Delay Effects

Sequencer Delay Masterclass
Published July 2003
By Paul White

Although delay can be one of the most simple studio effects, software delay plug-ins often provide a bewildering array of options. So we take a look at what all the sliders and switches do, and provide advice on how best to use them.

Today we're exposed to so many sophisticated studio effects, both as hardware and in the form of plug-ins, that digital delay can seem a little tame, but in reality it's still one of the most commonly used effects after reverb. Until the invention of the tape-loop echo box, delay meant nothing to a musician other than a drummer turning up late, but once it had appeared there was no going back, and the effect soon became part of pop culture. Ironically, we all used to complain about tape echo units — they never ran at a steady speed, so the pitch wavered, and the delays weren't as bright or as clean as the original sound, so the repeats became progressively more distorted and distant.

After a brief flirtation with analogue 'bucket brigade' echo devices (which sounded rather dull), the DDL (Digital Delay Line) arrived on the scene, and finally delivered what we'd all been asking for — rock-solid, clean repeats. The trouble was that once we'd got this degree of technical perfection, we realised it didn't sound as 'musical' as our old tape echo units, so before long designers started to think up ways to add in the distortion and pitch wobble that characterised the tape echo sound. This is relatively easy to do in the case of plug-ins, where extra controls don't add to the manufacturing cost. Another thing that plug-ins do well is synchronise to the tempo of the host software, so setting up delays that run exactly in time with the music has never been easier.

The Principles Of Delay

The concept behind a digital echo device is quite simple. A signal is passed through a memory buffer, where it is delayed for a short time and then sent to the output. Mixing the delayed sound with the original signal produces a single repeat following the original sound, but feeding a percentage of the delayed signal back to the input produces a repeating echo effect, where each subsequent echo is a little quieter than the previous one. The feedback gain must be less than unity, however, otherwise the echoes will build up in level rather than decaying, resulting in an uncontrollable howl. A popular dub trick is to keep adjusting the delay feedback level so that it starts to build up, then, just as it threatens to get out of control, the feedback level is reduced again. Plug-in automation makes this very easy to do using plug-ins.

The next level of sophistication is to provide two or more outputs from the delay line at different delay times. A multi-output delay line is said to be multitapped, because the signal is 'tapped' off at different points in the delay buffer. A delay line with three or four taps is better able to emulate the old tape echo units, most of which had three or four playback heads, and by applying feedback (which was usually based on a mix of all the heads), the complexity of the delayed signal becomes far more intense, as the different delay times lead to a more chaotic build-up of repeats.

While tape delays were invariably mono-in/mono-out devices, software delay effects can be made either mono or stereo, and the different tap outputs can be panned to different positions to create a wide, stereo effect from a mono source. The so-called ping-pong delay takes this concept one step further by using two delay lines, one fed to the left output and one to the right. The feedback from the right delay line is returned to the left input and vice versa, so that instead of the echoes always coming from the same pan position, they appear to bounce from side to side as the repeats come alternatively from the left and right outputs. Ping-pong delay is a commonplace commodity in the plug-in world, but is no less effective for that.

In order to emulate the sound of tape delays, some plug-ins allow the feedback signal to be filtered, usually to reduce the high end, but it's not uncommon for both low and high filters to be available. There may also be a way to apply either regular or pseudo-random pitch modulation to the delayed signal to simulate the wow and flutter of an old tape delay. A further nicety not often provided is some way of adding distortion to the feedback signal so that the repeats become progressively duller and more distorted. The reason this sounds more musical is that less well-defined repeats don't conflict as much with the original sound, and as they become duller and less well-defined after several trips around the feedback loop, they appear more distant sounding.

Modulated Delays

In the early days of DDLs, before programmability became commonplace, everyone knew how to set up chorus, flange and phasing effects by modulating short delay times and applying different amounts of feedback, but today these effects all tend to come as separate plug-ins, so some newcomers to recording may be unfamiliar with these basic principles.

Perhaps the most common modulated delay effect is chorus. Chorus approximates the effect of two or more instruments playing the same part, and is frequently used on guitar and keyboard pad parts. It works using a delay of just a few tens of milliseconds, modulating the delay time at around 3Hz using an LFO (Low Frequency Oscillator). If delay time is modulated, the pitch of the sound is also modulated. The direct and modulated/delayed sounds should be mixed equally so that the listener perceives the differences in timing and pitch as being two slightly different renditions of the same part. Some chorus plug-ins use a multi-tap delay line, so that several pitch-modulated copies of the original sound are combined for a richer layered effect.

Logic's ensemble plug-in.Logic's ensemble plug-in.By further shortening the delay to just a few milliseconds and using only the delayed sound, modulating the delay time has the effect of producing a pitch vibrato. If the delay time is less than around 15ms, the listener won't usually perceive any delay, so most chorus plug-ins that have a mix control can be used to create vibrato simply by setting them to 100 percent effect. A general rule is that, the longer the delay time, the less modulation depth you need to create the same degree of pitch modulation.

It is a short step from vibrato to phasing, as all you need to do is reduce the modulation rate and add in the dry signal. The concept is similar to chorus, but because the delay time is much shorter, there's no audible delay. Instead, the two signals combine such that some frequencies add while others cancel, producing a comb-filtering effect, and these frequencies change as the delay time is modulated. Subjectively, the result is similar to mild flanging, but less dramatic. Phasing is popular for use on guitars and electric pianos, but may be applied to almost any instrument. Adding feedback and increasing the delay time slightly produces flanging, a heavily comb-filtered 'whooshing' sound born in the psychedelic era.

Delay Effects in Emagic Logic

Logic's simplest delay plug-in, Sample Delay, isn't so much an effect as a tool, as it adds delay in single-sample increments to either or both channels of a stereo signal. The linked mode can sometimes be useful for compensating for a delay elsewhere in the system, whereas the independent left/right mode is handy when you need to get the two halves of a stereo track back into line or where you're combining a mic and a DI signal and need to get the best subjective result when they combine. As Logic doesn't support sample-accurate audio track editing and positioning, this plug-in could be used to get around some of the limitations this causes by allowing timing offsets to be adjusted in single-sample increments.

The next delay is Stereo Delay, which has independent delay times for the left and right signal paths, as well as two sets of feedback controls, one operating normally and one set feeding into opposite channels for creating ping-pong delays. Sliding high-cut and low-cut filters are available in the feedback path, and delay times can be directly (and independently) sync'ed to one of four note values and then further modified via the Groove slider for tempo-related effects. This latter control has sufficient range to allow triplet delays and other multiples to be set up.

Logic's tape delay plug-in.Logic's tape delay plug-in.Logic's Tape Delay is based on a single repeating echo, again tempo related and with high-cut and low-cut filters, but this time further controls have been added to modulate the pitch of the delayed sound. An LFO-controlled modulation allows gentle chorus effects to be applied to emulate the 'wow' of a worn tape transport, while Flutter Rate and Flutter Intensity simulate the higher-speed pitch fluctuations that would have been caused by worn capstan bearings or worn tape. Used carefully, this comes very close to the original tape echo sound, but the fact that there's only one 'head' means you can't recreate some of the classic guitar effects that were originally produced using three-head and four-head tape delays. However, you can get close to it by putting a Tape Delay and a Stereo Delay in series.

The final Logic delay is the Modulation Delay, a single-tap, 'feedback and mix' affair with two LFO modulation oscillators that can be mixed in any combination and set to run at independent rates, where the overall modulation amount is controlled via the Width slider. The delay time is manually adjusted — no tempo sync this time. A further slider is included for volume modulation, so that tremolo can be incorporated into the effect, plus there's a button that switches between conventional modulation and a special mode that is designed to remove the obvious pitch fluctuations that delay modulation normally causes. Additionally, there's a separate Flanger/Chorus stage where one knob morphs between chorus and flange effects while the other sets the stereo phase of the effect, allowing the left/right sweeps to be aligned or delayed relative to each other for more stereo interest. The result is a delay with a chorus/ensemble character that works particularly well on electric guitars, and that can give mono sources a spacious, stereo feel. If you want to experiment creating modulation effects of your own, this is the plug-in to try first.

Logic's phaser plug-in.Logic's phaser plug-in.Logic also includes a number of modulation effects, though here I'll be concentrating only on its modulated delay effects, which excludes the rather wonderful Tremolo and Spreader plug-ins. Logic offers one really simple Chorus effect, with only width, intensity and speed controls, plus the more spectacular Ensemble. Ensemble is a multitap chorus offering up to eight voices controlled by two LFOs and a random signal generator, where the contribution and modulation rate of each of these three sources can be adjusted using separate sliders. Stereo Phase and Stereo Base controls allow the width of the effect to be adjusted (again by offsetting and panning the left and right modulation sweeps).

By contrast, Logic's Flanger is extremely simple, but it sounds no less effective for that. It has a simple four-slider interface with controls for mix (which is normally left set at 50 percent for both chorus and flange effects), Intensity (modulation depth), Speed (modulation rate) and Feedback. That leaves only the Phaser, which is a little more elaborate than usual in having two combinable LFOs, plus frequency sliders to set the limits of the sweep range. There is also an Order control to emulate the number of phase-shift stages employed, where more stages produce more notches in the frequency response. Again the familiar Stereo Phase control puts in an appearance. Paul White

Delay Effects in Digidesign Pro Tools

Sequencer Delay Masterclass:The Digirack II plug-in package bundled with Digidesign's MIDI + Audio sequencer software doesn't contain individual plug-ins for delay-based effects such as chorus, phasing and flanging. It does, however, include a selection of well-equipped Mod Delay plug-ins, which can be used to create all these effects as well as conventional delays. Short Delay, Slap Delay, Medium Delay and Long Delay used to be supplied in both TDM and native versions, depending on what kind of Pro Tools system you had; from Pro Tools v5.3, all run in the native HTDM or RTAS formats, but none of them use a great deal of processor power. All are available in mono, mono-to-stereo, multi-channel and multi-mono versions, the stereo versions offering separate controls for the left and right delay paths.

In each case, the settings on offer begin with an input polarity switch and an input gain control if your patch uses a lot of feedback, the latter can help prevent overloads. Following this is a conventional Mix control and a cutoff control for a simple low-pass filter, which allows you to darken the delayed signal to create 'tape echo' effects. After this come the Delay time slider, modulation Depth and LFO Rate controls, and the Feedback setting.

The only difference between each of the Pro Tools delay plug-ins is the maximum delay time available, which means you have to choose the right plug-in for the particular delay-related task you have in mind. For a detailed explanation of what you can achieve with all the different plug-ins, including how to create all the conventional delay-based effects, check out Simon Price's Pro Tools Notes column from SOS November 2002. Sam Inglis

Using Delays

Delays and echoes are useful both on vocals and instruments and, in most cases, setting the delay time to a multiple of the song tempo helps reinforce the rhythm of the song. Tempo sync facilities make this very easy, but be aware that any tempo changes in a song can cause tempo delays to hiccup quite badly, so it may be best in such cases to split the part into two tracks at the tempo change point and use two different delay plug-ins set appropriately to the tempo of each section. You can use the delay sync mode to establish the delay time value needed for each section, then flip to manual mode and enter the time values you noted down. By working in manual mode, you won't get any unpleasant surprises as parts hanging over from the first section spin 'off pitch' as the delay time suddenly switches. Some of Emagic Logic's delays include a smoothing parameter hidden away in the extra controls section (press the button with the binary numbers in it) designed to make the delay time change more progressive when tempo changes are encountered, but in practice, this just makes the transition take longer and doesn't make it sound any less messy.

One very common production trick is to add echo only to certain words or phrases in a vocal part, which is best accomplished by turning up the echo or aux send control just before the phrase occurs and turning it down again immediately afterwards. Using your sequencer's automation capabilities, this can now be done very precisely.

Many rock singers use a short, slapback delay, created by setting a single repeat and then adjusting the delay time so that it follows immediately after the original sound, but not so closely that it blends into it. Artists such as John Lennon and Elvis made extensive use of slapback delay, but it also works well on some guitar parts. Artificial Double Tracking (ADT) is also based on short delays, but with a little added pitch modulation. It isn't as good as tracking the part twice, but it is a useful effect nevertheless. In most cases, some reverb would also be added to delayed vocals.

Chorus creates a lush, full sound, but it also has a habit of making the processed sound sit further back in the mix, which is why it's so often used on synth pad and acoustic guitar parts. I don't like the sound of chorus on vocals, though flanged vocals can work in certain circumstances. Chorus is best suited to string parts, keyboard pads, electric guitar and electric fretless bass where multi-voice chorus plug-ins produce the most complex textural results. In the early days of recording, all kinds of tricks were used to make the chorus effect appear to be in stereo, but with many modulation plug-ins, you get a stereo output automatically, where the phase or width control regulates the stereo spread of the sound. Paul White

Delay Effects In Steinberg Cubase

Three simple delay-based plug-ins were originally bundled with earlier versions of Cubase VST, and are still available as an option when installing Cubase SX if you need them for compatibility with older songs. All feature the generic 'one slider per parameter' interface, but SX users don't seem to get any presets for them. However, if you save the default banks from within Cubase VST you can then load them into the SX versions.

Stereo Echo provides separate delays for the left and right channels, each with its own feedback control, plus a link control to turn it into a mono delay. Choirus occasionally suffered from clicks and distortion, and was later replaced by Choirus2, but as far as I can see both are now identical in their SX incarnations, and are capable of a wide range of pleasing chorus and flange effects. Without tempo sync and graphic interfaces all three of these plug-ins are much trickier to set up than their replacements, but in their favour they do use a tiny amount of CPU.

Along with VST Instruments, tempo sync arrived with the VST 2 specification, first seen in 1999 on Cubase VST v3.7 on the PC (and v4.1 on the Mac). However, it wasn't until the following year that Steinberg managed to get the Mac and PC platforms 'in sync', with the release of Cubase VST v5.0, and this also saw a new 'modernised' graphic look and a bundle of fourteen new plug-ins.

These have once again been updated for Cubase SX, and include Double Delay, which, as its name suggests, offers two delays, each of up to ten seconds. Each has a pan control, plus optional tempo sync. When tempo sync is activated you get straight, triplet, and dotted options from 1/32 to 1/1 for the base note value, and then a separate note value multiplier from x1 to x10. It's a bit difficult to get your head around the first few times, but things soon drop into place, especially with the dragable graphic display of pan and multiplier settings.

Mod Delay only provides a single delay, with identical delay time and tempo sync options, but makes up for it by adding control over the rate of pitch modulation for the delay effect. You can use this to set up chorus and flange effects with short delay times (although this is easier using the dedicated plug-ins), but its main use is to add movement to longer delays.

The Karlette plug-in within Steinberg's Cubase SX provides a powerful recreation of a multi-head tape-delay unit.The Karlette plug-in within Steinberg's Cubase SX provides a powerful recreation of a multi-head tape-delay unit.Karlette is essentially a souped-up tape loop emulation with four delay channels. Each 'tape head' has its own set of controls, but a global Sync button lets you switch between a delay of up to 2 seconds, and note values ranging from 1/32 to 1/1, including triplets. Each head has its own Volume, Pan, Feedback, and Damp (low-pass filter) controls, and some quite complex effects are possible, although it's a shame that no 'wow and flutter' options are available.

The Chorus, Flanger, and Phaser are capable of some rich effects. Chorus has Delay and Frequency controls that are also displayed in a graphic window where they can be dragged by the mouse, and there are three modulation waveforms available — triangle, ramp, and pulse. In addition, the Stages knob can add up to three delay taps in Cubase VST v5, and four in Cubase SX, for a really rich multi-layered chorus.

The Phaser is somewhat more complex, with tempo sync options for its Rate control, along with an overall Feedback control, plus a handy Stereo Basis knob that controls stereo width. Left at its default 50 percent setting, this retains the width of the original signal (if stereo), while increasing it provides enhanced stereo separation and zero drops it right down to mono. Rate, Feedback, and Stereo Basis can also be set by dragging in the graphic display.

The Flanger also provides Stereo Basis and Tempo Sync options, and Delay times from 0-100mS, but is rendered far more versatile by the inclusion of the Shape Sync knob. At its middle setting this provides a triangle waveform, but by moving it to the left or right you can progressively modify its symmetry all the way to ramp down and ramp up respectively. This means you can sync flange sweeps to each note — especially effective with snares and percussion.

Two more delay-based plug-ins are to be found in the SX modulation folder. Symphonic combines a stereo enhancer and an auto-panner with a simple delay/depth/rate chorus stage, to provide some rich swirling motion effects. Finally, Paul Kellett's Rotary is a Leslie speaker simulation, and so doesn't strictly speaking fall into the delay category. However, since it's bundled with Cubase and provides a variety of chorus and flanging effects it's worth a mention, especially since it has loads of controls.

One thing I've found with all the various Cubase delays is that they continue after the song stops, which would normally make sense, to capture the echoes after the final note finishes. However, you may have to turn the plug-ins off and then on to permanently silence long feedback delays.

Delay Effects In Cakewalk Sonar

Like Cubase, Sonar has a set of older and rather more basic-looking delay plug-ins for compatibility purposes. Flanger, Chorus, and Delay are identical in appearance, comprising separate Left and Right Delay length controls with an optional Link switch, and Left and Right Feedback controls, along with Cross Feedback for ping-pong effects. An LFO is provided for modulation duties, with Depth and Rate controls and a choice of triangle or sine waveforms, and the plug-ins are completed by Dry and Wet Mix controls with an optional Link switch and an overall Bypass switch.

The only difference between the three, apart from the included presets, are the delay ranges: the Flanger ranges from 1-20mS; the Chorus from 20-80mS; and the Delay from under a millisecond all the way to five seconds. Despite their bland appearance, all three are surprisingly capable. The three feedback controls make the Delay very versatile, while the LFO is very useful on longer delays for radical echo pitch-bend effects. The Flanger can provide a wide range of through-zero effects, although beware of trying out extreme feedback settings, since they can cause a sharp crack through your speakers followed by silence (mercifully this is a plug-in fault rather than cone damage). The Chorus can add anything from subtle thickening to stereo spreading, and all three plug-ins provide a useful set of embedded presets to get you started.

The same three effects are also handled by newer offerings from the DSPFX range, this time with much smarter graphics and automatable controls, although once again the interfaces are surprisingly similar apart from a choice of green livery for the Fxflange, blue for Fxchorus, and red for Fxdelay. Sadly, they also have a similar approach to the EQ that I described in May's EQ masterclass — each 'voice' has an overall gain control, and can be separately enabled, but the remaining controls are shared, requiring you to activate the appropriate voice select button before altering them. While this provides an incredible amount of control, and avoids having 20 to 30 controls on screen, it's convoluted and difficult to use since you can only ever see the current values for one voice at a time.

The Fxflange is the simplest, providing two voices, each with its own gain control and on/off switch, along with a select button to access the four extra sliders alongside, controlling Delay, Feedback, Pan, and Mod Freq. Having separate pan controls for each delay lets you adjust stereo spread, and this is a versatile plug-in with plenty of useful bundled presets.

Fxchorus provides Delay, Mod Depth, Pan, and Mod Freq for its four global parameters, and this time there are four voices for some really rich effects. However, this also doubles the frustration during editing, especially since you can't cut and paste settings between the voices. However, there's no denying that Fxchorus sounds good, and with 35 presets you may not have program your own sounds.

Fxdelay is once again capable of many versatile and good-sounding effects, but suffers even more from the interface, since there are both Course and Fine delay controls, and there's no read-out of the combined value. The lack of any tempo sync also makes setting up the four voices frustrating, especially as this plug-in is far more likely to require its delay controls adjusting to suit the tempo of each song. However, because the four voices have separate Feedback and Pan controls, they are capable of some clever multitap effects, such as stereo delay sweeps, as long as you have the patience to set them up. Martin Walker

Delay Effects In MOTU Digital Performer

Chorus can create effects from the subtle to the downright nasty, and also does duty as a vibrato plug-in. All the expected chorus parameters are present, with delay time modulation being controlled by the Tempo Lock section and the Depth knob. However, Chorus's modulating LFO can't be set to anything other than a sine wave. Although a mono-in/mono-out Chorus is available, the stereo-out versions are more flexible, since wet and dry signals can be panned separately. Pan them wide apart for spacious stereo, or both to centre to achieve flanger-like effects. The 'through zero' option allows Chorus to apply delay to the dry signal as well as the wet, so at times the wet signal will actually be heard first. For vibrato, turn the Mix control to 100 percent and then use Tempo Lock and Depth to dial in as much as you need. Bear in mind, though, that greater modulation depth can be applied to more delayed signals, so the Delay parameter has a real bearing.

Sequencer Delay Masterclass:Sequencer Delay Masterclass:

Delay is ideally suited to producing rhythmic stereo (and surround) ping-pong delays, with feedback paths both within and between its channels. Because of the very real risk of rampaging feedback, Delay's most important control is probably its Panic button, which immediately silences its output and clears all the delay buffers. Extra flexibility is afforded by each channel's multi-mode filters - great for analogue simulations and more creative effects. Feedback can be produced both in phase (positive values) and out of phase (negative values). For more about this great plug-in see Performer Notes in SOS July 2002.

Flanger has many similarities to Chorus, but crucially does away with the wet and dry pan parameters, and adds that essential Feedback knob. Delay times of below 5ms produce 'classic' flanges, whilst nearer the maximum of 20ms, and with high depth and feedback values, various sci-fi effects can be teased out. The Mix control is quite important too, as it allows delayed signals to be mixed both in phase and out of phase for subtle differences in tone. More sonic variation is provided by the L/R In Phase button, too. When it's not selected, the delay time applied to one channel will be comparatively short whilst the other is long, and vice versa. It's like having separate, opposed flangers on each channel, and it sounds groovy (man).

Phaser is a simple plug-in, with the intensity of the effect set using the Depth knob, and the bandwidth of the resultant notch filters controlled by the Width knob. The Tempo Lock section, as ever, controls the speed of the modulating LFO, and there's an L/R In Phase button here too, for yet more psychedelic entertainment.

By comparison, Echo is quite complicated, though in essence what it does is very simple. It's a four-tap design with separate gains for each delay path, and a global feedback path. It's suitable for applying conventional delays using just one tap, or for setting up rhythmic patterns using all four. The global feedback even allows bizarre pseudo-reverb tails, or endlessly ticking echoes.

Finally, though not a dedicated delay plug-in, Sonic Modulator has a lot to offer, because it has a flanger-like Delay section preceded by a dedicated vibrato module. What makes it better than Flanger or Chorus is the open-ended modulation scheme, with multiple multi-pattern LFOs. A versatile filter, crossover and amplifier section just adds to the fun. For more on Sonic Modulator see Performer Notes in SOS October 2002. Robin Bigwood

Published July 2003