The Funk Is Alive With the Sound of Envelope Filters

Envelope filters have long been an excellent, if infrequently used device in the guitar player’s toolbox. They can add thick layers of funk or mild harmonic interest to a track by being touch responsive and vowel-like in their manipulation of the guitar’s sound. Lengthy analysis about what an envelope filter does can be found here, but nothing really conveys the beauty of an effect like real world listening examples. We’ll look at some songs that feature envelope filter along with some ideas on how the effect is being used. Load up your favorite music streaming service and prepare to get quacking.

Grateful Dead

“Dancing in the Streets”

Cornell University - 5/8/1977

Envelope filters and late 70’s Grateful Dead go together like peas and carrots. This particular show from Barton Hall at Cornell University is widely regarded as one of the best among Deadheads and for good reason. There’s a palpable energy on the recordings and the jams are tight, funky, and exploratory.

Most importantly, the second set is loaded with envelope filter. Jerry Garcia was known for using a Mu-Tron III, which would still have been a fairly new effect at the time, having only been introduced in 1972 by Musitronics.

The Mu-Tron III, as well as many other envelope filters that have followed, allow for the envelope direction to be switched. We most commonly associate the envelope filter quack with a “wow” sound, which is found with the “up” setting. This means the filter is essentially closed when idling and then opens up when triggered by the amplitude of the guitar’s signal. However, the “ow” sound that is found in the “down” setting, starts with a wide open filter, closes down when a signal passes through, and then opens back up as the signal decays.

Most of the tracks from this show that utilize the envelope filter show it doing its usual thing with the up setting engaged, but this track features the envelope filter in the down mode through a big chunk of it. The beauty of using the filter in this direction is that you get a hard attack with each note before the filtering kicks in. This leads to a plucky, funky sound unlike anything else.

The effect is used through most of the recording. Around 4:10 Jerry starts to rip into it, but with fairly delicate picking. You can hear how the effect changes as he starts picking harder around 4:45 and the filtering starts to sweep lower, making the effect even more pronounced and the guitar darker overall. To my ears this whole track sounds like it’s set in bandpass filter mode as we don’t get a ton of low end on his lead tone, but as he’s also playing mostly in the higher registers it’s a little hard to be 100% certain that it isn’t in low-pass mode.

This whole show is well worth listening to, but this track exemplifies a lesser used set of sounds available with an envelope filter. To hear a more typical envelope filter usage, check out “Estimated Prophet” or “Fire on the Mountain” from the same show.

Edie Brickell and New Bohemians

“What I am”

Shooting Rubber Bands At The Stars

This track from 1988 tends to be a love it or hate it tune for a lot of folks. It’s got a cool and simple groove, lyrical content that would likely be heavily dissected in an undergraduate philosophy paper, and a solo in the middle that has some delicious, crunchy envelope filter.

At about 2:10, guitarist Kenny Withrow tears it open. The brand and model of the pedal being used does not seem to be documented. We could speculate, but it doesn’t really matter. Whatever the case, it’s set as a low-pass filter in “up” mode for the classic envelope filter quack sound.

One of the cool things about this track, is that it offers a pretty condensed look into some of the sonic changes available with an envelope filter within the confines of one particular setting. As the solo builds, the picking gets harder and the filtering becomes more pronounced. However, it also gets more crunchy.

This is common with envelope filters. The filter circuitry itself can get slightly overdriven as one picks harder, but the resonant peak also creates a bump that can overdrive an amp. Where a clean boost would juice up all frequencies to overdrive an amp across the spectrum, an envelope filter is only doing that around the cutoff frequency where the feedback occurs. This yields a kind of spectrally-selective overdrive.

Comparing the start of the solo around 2:10 to the peak of it around 2:36, you can hear the difference between the clean and gritty quack sounds.

The post-solo choruses feature filtered rhythm playing in the background and it showcases how the envelope filter is not just for vowel-imitating lead lines. Rhythmic guitar parts through an envelope filter take on a personality similar to a lot of the background synth lines in Talking Heads tunes like “Burning Down the House.” It allows the guitar to have more of a stab quality that you might expect from horns or synthesizers, but in a less aggressive manner.

Parliament

“Night of the Thumpasorus Peoples”

Mothership Connection

Bootsy Collins is almost always mentioned in discussions about bass, envelope filters, and/or funk so it’d be wrong to leave him out of this one. Parliament’s “Mothership Connection” is one of my favorite albums of all time and is, of course, one of the funkiest collections of music, specifically designed for improving your interplanetary funksmanship.

When one starts messing about with envelope filters it’s easy to get sucked into a mindset of throwing it on everything to make it more funky. Their compelling vocal quality, the spank of a quickly closing envelope, and the ability to tame some of the high end all work together to make it the ultimate funk machine. So we should use it on every track, right?

Not at all.

That’s part of what makes Bootsy’s sonic choices so excellent on this album. The opening track, “P-Funk” does feature some envelope filter on the bass, but not all the way through. If it is on all the way through, the sensitivity is way down so that it only engages at certain points. In fact, many of the tracks on the album are just straight-up thumpy bass with no filtering happening at all.

With a lot of synths and phaser-laden guitars happening across the album, it’d be too much to also have quack bass for 39 minutes straight. But when tastefully used, it offers some extra ear candy on top of the groovy bottom.

What makes envelope filter so cool on bass is that the filtering doesn’t cut out the entire signal when set to be less sensitive. This means the sweeping and removal of higher frequencies isn’t super noticeable on notes played in the lower registers, but it is noticeable in the higher registers. On this track the filtering is really only heard when he goes for the occasional fill higher up the fretboard.

This selective, but careful use of envelope filtering makes it special when it does happen, but also doesn’t overload the listener with too many dynamic sounds to process. It also leaves room for the synths and horns to enjoy some wiggle room in the spectral landscape.

Frank Zappa

“Stink Foot”

Apostrophe

In hindsight, it’s pretty clear that those mid-70’s Zappa albums aided in the development of my taste for vintage electric pianos, analog synthesizers, weird bands like Phish, and envelope filters on guitars. Being aggressive in his sonic choices, sometimes it can be hard to discern on Zappa records the difference between wah, filter, and even phaser.

The solo section in “Stink Foot,” to my ears, sounds distinctly envelope filter. For one thing, rocking a wah that quickly would likely cause one’s foot to fall off after a single take.

The envelope filtered section starts around 2:18 and there’s a lot going on there. I can’t tell if it’s double-tracked or delayed, but there are definitely discreet note attacks when comparing the left and right stereo channels. It is also possible that the signal was split before the pedal and we’re hearing some dry sound blended in. Being devoid of low-end, it sounds to my ears like the Mu-Tron is on the bandpass setting.

This particular solo shows some drastic differences in playing dynamics, note decay, and the envelope’s response to that. The solo opens with long bent notes, yet around places like 3:12 we hear a bunch of notes being thrown down quickly and the filter is doing some pretty rapid opening and closing.

This is an interesting track for an envelope filter example as there’s no element of “funk” to it. It’s got that quintessentially mid-70’s Zappa production, with a feel that’s more of a wistful rollicking instead of some on-top-of-the-beat funk jam. However, the quirkiness of the envelope filter is an appropriate choice to support a song about stink foot and talking poodles.

John Mayer

“Wildfire”

Paradise Valley

In a discussion of envelope filter listening examples, John Mayer would probably seem a more obvious choice in 2019, given that he’s been playing with Dead & Co for the past few years. However this track from 2013 predates his Dead gigs and features the tasty guitar playing and widely varied guitar tones that Mayer brings to most of his work.

The opening groove of this track sounds like an ambiguous mix of sounds and licks you’d hear on a country record, but also maybe on a Dirty Projectors song. Most of the tune is fairly harmonically simple until he drops some of those Berklee jazz chords into the middle of it. Around 2:52 it’s time for another change and we get some tasty envelope filtered guitar.

Where the envelope filter shines on this track is that it removes the hard edge from the sound as we cruise out. A lot of the other guitar sounds and grooves are pretty percussive in this track. By going with a “wow” filter sound that is neither overly sensitive or resonant, it takes us out with a slinky, vocal guitar thing with a soft attack. Had he gone with a hard-edged, overdriven, rock-song-climax solo sound, it might be sensory overload. The envelope filter gives us something to latch onto, but it’s mellow and easy and a nice contrast from all the other parts of the tune.

Grateful Dead

“Shakedown Street”

Shakedown Street

This is one of the most famous envelope filter tracks of all time. It’s dark and funky and the interplay between the lower register filtered guitar and the higher register chords lays down a very danceable groove.

This would have been a MuTron III and this time it’s set for the more frequently used “up” mode with the low-pass filter setting. To my ears it sounds like the resonance/peak is dialed pretty far back on this track as it’s not so sharp and biting; it’s got a little more of a growl to it.

The high part has something going on as well, but to my ears it sounds more like a slowly rocked wah than an envelope filter. Full transparency, I can’t tell with 100% certainty. Sometimes in upper registers and especially at higher sensitivity settings, envelope filters don’t immediately close back up so you probably could manipulate one to behave like it does on that track.

The use of non-envelope filtered guitar as the track closes out is a nice contrast to the heavily filtered grooves found in the rest of it. This continues the theme that with great envelope filtering comes the great responsibility to not overuse it.

Responsible Envelope Filter Usage

Envelope filters are not widely deployed into every track in every genre the way overdrive and delay might be and it would be sonically inappropriate if they were. Much of the filter’s intrigue is in its slightly rare usage. The vocal quality and touch sensitivity make it one of the most unique and dynamic effects. While it may not be an “always on” pedal, it’s a wonderful tool to have on the pedalboard when you need to offer an extra nugget of ear candy for the listener.