In a livestream on April 7, 2020, titled "Making a 'Reanimation' themed song LIVE," Mike Shinoda uses the Soundtheory Gullfoss plugin, as seen on the Shinoda Livestreams YouTube channel.

One of five plugins featured in this July 20, 2020 video, at 0:46.

So I'm going to start by talking about my latest obsession. I just discovered this plugin a few months ago and I've been putting it on everything: Gullfoss by Soundtheory. This is, like, just a magical plugin; it brings out a lot of clarity and detail, it tames things that are too harsh... So let me play a quick example. (...) Gullfoss is on the master channel by the way. (...) I find this almost every time I use Gullfoss. I feel like I've got a mix pretty good mix going and then I throw it on the 2 buss and it's like "wow! That's way better."

You can see it open on his monitor.

In this video at 23:16 Bruce shows Gullfoss EQ

At 4:44, you can see him using Gullfoss

Used for vocals on Twice as Tall, including lead vocals on "Time Flies", as stated by mix engineer Jesse Ray Ernster in this June 2021 Sound on Sound interview.

“The song already felt great after a few minutes of mixing,” Ernster continues. “The reference mix felt good, the beat was solid too. As I mentioned earlier, after that it was a matter of getting the vocals to shine. Dialling in the vocals took quite a bit of time on this song, because there were so many of them. This song was all about the backing vocals, getting them to sit in a place where they can shine and sparkle and just sit perfectly.

“Pretty much every background vocal on the song has the CLA Mix Hub channel strip, doing some high‑pass filtering, some EQ, and compression. I approached this mix a bit like a console mix, and dialling in every background vocal with the Mix Hub got them where I wanted them to be. I did not need 10 plug‑ins to make the background vocals sound good. This plug‑in just lit them up.

“One interesting moment with the backing vocals is in the bridge of the song. Diddy had a vision that these ‘welelel’ vocals would not only be wide but would also be wrapping around, with the panning going from left to right. So I put on the Waves S1 Shuffler, turned up the width knob and then automated the panning. It was a bold Diddy move that really paid off. It became a special moment, and is one of my favourite spots in the song.

“Underneath the ‘welelel’ track are nine backing vocal aux effect tracks, which are a ModDelay 3; 16th‑note, eighth‑note, quarter‑note and half‑note delays (all the Valhalla Delay); a ping‑pong delay (Waves H‑Delay); and all those tracks have sends to a Valhalla Vintage Verb plate and the FabFilfter Pro‑R. And all those feed the BGV FX bus. I was just moving these effects all around until they felt right.

“Burna’s main lead vocal is in red. One technique I learned from my dad is to ride the fader on vocals, so you don’t get the anomalies that you can get when compression is applied to a recorded voice. As I don’t have a fader, I chopped up the vocal and then adjusted the Clip Gain for each phrase. As for processing, I added the Gullfoss EQ, that kind of rides the frequencies, and which I love. I used it on Burna’s voice on most of the album. There’s also a Pro‑Q 3 to notch out some frequencies, and the Acustica Amber 3 EQ, which adds the most gorgeous top end.

“There’s a send on the main lead vocal to an aux with the Soundtoys Devil‑Loc, adding parallel distortion. It’s a bus I try once in a while. If the vocal is sitting where I want it to sit in the mix volume‑wise, but it needs a little bit more glue, body and warmth, I’ll go for the Devil‑Loc. It brings the vocal straight up into your face. If you want a pop vocal that is right on top of everything, this is it.

“I also have other vocal aux effect tracks, ie. different delays, reverbs, pitch‑shifts. I generally do not use reverbs on the lead vocal, but only delays, because they take up less space. Then I’ll have a delay to feed a reverb that can sit in the background. The pre‑delay creates this ocean of ambience that does not take away from the intimacy and upfront nature of the lead vocal.

“There are a couple of tracks called ‘Throw’, and I create those by dragging duplicate audio to a separate track, and then putting an effect on with the mix at 100 percent, in this case Valhalla Delays. I don’t really like using automation on sends and muting and so on, as it’s a really slow workflow. It takes one second to drag down some audio, add a delay and done.

“Below the ‘Throw’ tracks are two Time Adjuster aux tracks and a Valhalla Space Modulator aux track. Together they recreate the Eventide H3000 wide vocal effect. The Time Adjuster plug‑in delays the left and right channels a bit, and one channel has the CLA MixHub to add some distortion and the other channel has the lo‑fi. The Valhalla Space Modulator is followed by a Cranesong Phoenix II, driving really hard in Dark Essence mode. These three go to an aux called ‘SHIFT M’, and it turns a mono vocal into a wide, enveloping, beautiful vocal. Also, there’s a ‘Lead Vocal All FX’ aux with the Pro‑Q 3 EQ that takes out all top and bottom, which you don’t need on vocal effects.”

At 2:32 into the video, YMIR is shown to be using the Gullfoss VST