We delve into the mysteries of envelope following in Ableton Live.
An envelope follower lurks under the hood of each of Live’s dynamics processors. It detects the audio level on which the rest of the circuits base their compressing, limiting or gating action. This month we’ll look at a variety of applications for envelope followers beyond controlling dynamics. I’ll start with a quick look at other Live effects that incorporate an envelope follower and then discuss several ways to use the stand–alone envelope followers available as Max For Live devices.
Four Live audio effects have a built–in envelope follower dedicated to modulating a single parameter: Auto Filter (Filter Cutoff), Dynamic Tube (Bias), Flanger (Delay Time) and Phaser (Frequency). Each effect’s Envelope knob is a bi-directional modulation–amount control, and the associated Attack and Release knobs affect the rate at which the modulation tracks the increasing and decreasing level. Except when using Auto Filter’s side–chain input, these envelope followers track the level of the signal being processed. Three of them (Dynamic Tube is the exception) have an LFO to modulate the same parameter as the envelope follower. With the envelope follower the modulation follows dynamics, whereas with the LFO it follows a random or waveform–based pattern. You can, of course, use the envelope follower and LFO at the same time. With a steady rise or fall in level, for example, the envelope follower will move the centre of the LFO’s range up and down as the level rises and falls.
Live’s Auto Filter, Dynamic Tube, Flanger and Phaser have built–in envelope followers (boxed in red) to control a single parameter. Auto Filter’s implementation is the most versatile in that it allows for side–chain input to the envelope follower. Here Auto Filter is set up for a variant of ducking: kick–drum hits momentarily raise the cutoff of a high–pass filter applied to the bass track to get it out of the way of the kick.
Take It To The Max
If you have Max For Live, which is included in Live Session, you’ll find two envelope followers in the Max For Live/Max Audio Effect section of Live’s Category browser: ‘Envelope Follower’ and ‘Max Api CtrlEnvFol’. A third alternative, ’REF’ ( 5 from k-devices.com), offers better graphics and advanced features (most notably a threshold control). Although their feature sets differ, each of these envelope followers works in the same way: you insert it as an audio effect device on the track playing the audio whose amplitude envelope you want to follow, and then you map the envelope follower’s output, which is a control signal, to the parameter you want to control. Although you insert it as an audio effect, the envelope follower has no effect on audio; the track on which it is inserted plays normally. An option to keep in mind is that you can insert an envelope follower on a Return track and thereby use it to follow the mix of the audio and instrument tracks sent to it (you’ll want to mute the Return track if you use this strategy). Follow these steps for a graphic look at how Envelope Follower works:
- Create two audio tracks, place a four–on–the–floor kick drum loop on one and a simple rhythm guitar loop on the other. Strums on the quarter–notes are a good choice for the guitar.
- Insert Live’s Simple Delay on a Return track and set its right and left delay times to two and three 16th–notes respectively.
- Play both loops and increase the guitar track’s Send knob to audition the effect of the delay without Envelope Follower.
- Insert Envelope Follower on the kick drum track, click its Map button and then click the guitar track’s Send knob.
- Start both tracks playing and observe the Envelope Follower display. You’ll see it clearly tracking the volume of the kick drum hits, and you’ll see the guitar track’s Send knob moving accordingly. You may or may not hear any of the Simple Delay effect, depending on the level and shape of the kicks.
- Note the two number fields adjacent to the Map button. They set the minimum and maximum values of the targeted control. Change the minimum (left) to 100 and the maximum (right) to 0. You’ll now hear truncated delays because the Send level traces the inverse of the kick envelope: it is maximum before the onset, drops quickly with the kick onset and then rises back to maximum as the kick decays.
- Return Envelope Follower to its default settings and create a modulation envelope for Envelope Follower’s Gain knob. Set the Gain modulation to 0, 3, 6, and 9 dB respectively for the four kicks. You’ll hear the delays rise accordingly during each loop of the kick.
- Finally, delete the modulation envelope and increase the Gain to produce nearly full–level envelopes on each hit. Now play with Envelope Follower’s Fall, Delay and Min settings. Their effect will be obvious.
Target Practice
As alternatives to modulating the Send level to Simple Delay you could modulate the Return track’s Track Volume slider, or you could move Simple Delay to the Guitar track as an insert effect and modulate its Dry/Wet knob. With both alternatives, Simple Delay will receive and process the full guitar loop rather than only the parts allowed through by the gyrations of the Send knob. Envelope Follower’s action will then modulate Simple Delay’s output; the amount of delay that is heard. The results are not as dramatic, but may be just what you want.
Many effects parameters other than level make good targets; reverb decay, filter resonance (Q), resonator gain and distortion amount, to name just a few. Keep in mind that it can make a difference where you place the envelope follower relative to the device it is modulating. If the envelope follower comes after the device and the modulation affects volume, that will influence the envelope follower’s action (because it follows volume). This can be useful, but when you want to avoid it, place the envelope follower before the device so that it follows the audio entering rather than exiting the device.
The Max For Live Envelope Follower audio effect is inserted on the Drums track with its envelope output mapped to the Send A knob on the Guitar track. The A Return track holds a Simple Delay set for two– and three–16th–note delays. The waveform graphics at the top show the guitar loop before and after Simple Delay without using Envelope Follower. The bottom waveform graphics show the results with the Envelope Follower settings shown above them.
The Instrument rack on the left holds piano and pad instruments in separate chains, and its Chain Selector is used to fade in the pad. The REF envelope follower on the right targets the Chain Selector (orange outline), and its Threshold is set so that no envelope occurs at lower volumes (yellow outline). REF’s Attack is set to smooth the onset of the pad (green outline).So far I’ve focused on effects processors, but instrument controls make equally good targets. One such application is fading instruments in and out, and if you have an Instrument rack holding different instruments, targeting the rack’s Chain Selector is one way to go about it. Another way is to use Live’s Crossfader to crossfade between instruments on separate tracks. To target the Crossfader, you’ll need to use Max Api CtrlEnvFol because it’s the only envelope follower that lets you select the target by menu, and that is the only way the Crossfader is accessible.
When One Is Not Enough
One feature none of these envelope followers offers is the ability to control more than one parameter. There are two workarounds for this. The most obvious is to use a separate envelope follower for each parameter you want to control. Because they pass audio through unaffected, you can arrange the envelope followers in series in the path of the audio whose level you want to follow, and that lets you see and edit them all at the same time. You’ll save lots of time dialing in the envelope followers’ settings if you enclose them all in a Group and then link their common controls using Macro knobs. On the other hand, you’ll want to avoid linking controls such as Min and Max for which you’ll probably want individual settings.
When the devices whose parameters you want to control are on the same track, you can enclose the devices in a Group and then map all the controls you want to target to a single Group Macro knob. You’ll be able to set the range of the Macro Knob individually for each targeted control so that the effect of the envelope follower will differ for each of them. Setting this up is a bit tedious, and envelope followers are not CPU hogs, so I prefer using multiple envelope followers whenever possible.
