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Inside Track: Trippie Redd 'A Love Letter To You 5'

Secrets Of The Mix Engineers: Koen Heldens By Paul Tingen
Published October 2023

Koen Heldens at Criteria Studio D.Koen Heldens at Criteria Studio D.

Working on Trippie Redd’s mixtape A Love Letter To You 5 at Miami’s Criteria Studios gave mixer Koen Heldens the rare chance to mix a rap album to half‑inch tape.

Trippie Redd’s fifth album Mansion Musik, released in January, didn’t quite live up to expectations, because it had been rush‑released after hackers had got hold of the sessions in progress. For this reason, mix engineer Koen Heldens was called in to make sure the final mixes for Redd’s subsequent mixtape, A Love Letter To You 5, were in the best possible shape. He conducted the mixes at Criteria Studios in Miami together with Redd’s regular collaborator Igor Mamet, who had recorded, co‑written and/or co‑produced almost the entire album. The end result features guest performances by top artists like Lil Wayne, the Kid Laroi, Roddy Ricch, and others, and is more a collection of ballad‑like love songs than a rap album.

Inside Track“We did two songs for A Love Letter To You 5, ‘Take Me Away’ and ‘Thinking Bout You’, at Criteria Studio A in June 2022, using the SSL 9000 J‑series in that room,” says Heldens. “We also did the Trippie Redd/Don Toliver standalone single, ‘Ain’t Safe’, in August in Criteria Studio E, which was released in October. Then I heard nothing for a while, until I was asked to mix the rest of A Love Letter To You 5 with Igor.”

According to Heldens, Criteria is Redd’s “studio of choice, particularly Studio E, where Lil Wayne recorded his Carter albums”. Heldens chose to work in Studio D for most of the mixing process, because its small size ruled out dozens of people showing up for studio sessions.

Bring The Bass

When not working in his home studio in Miami, Koen Heldens likes to take his gear with him. “I have acoustic panels in my room, and my gear consists of a maxed‑out Apple Mac Studio M2 Ultra, Apple Mac Studio Display, Apogee Duet 3 audio interface, Softube Console 1 system, Genelec The Ones 8831s with GLM Kit, Focal Listen Pro headphones and Apple AirPods Max. I am super mobile, and have a custom‑made laser‑cut PeliAir case for my Genelecs and GLM Kit, and custom laser‑cut hardcases for the Softube Console 1 system, which includes two fader packs, Mac Studio and Mac Studio Display.”

Heldens’ portable monitoring proved its value during the mixing process for Trippie Redd’s mixtape. “Igor and I worked for about two months in Studio D. On the first day we were working with the Genelec 1031s, Yamaha 10s and Augspurgers in the room, but although the room is very well balanced, for some reason I felt I could not judge the low end. The next day I brought in my Genelecs 8831s and used the GLM system to shut out the room. When we pressed Play, even the assistants were like ‘How’s it possible to hear sub out of those small speakers? It’s like having giant headphones on!’ So we could judge the low end better from there. The GLM system also showed the bump in the low‑mid area coming from the desk, and corrected that as well.”

Koen Heldens’ entire mixing rig is designed to be portable.Koen Heldens’ entire mixing rig is designed to be portable.

Tracking Out

Mamet and Helden’s process at Criteria D was to take the former’s rough mixes as a starting point, and then to continue working in his Pro Tools sessions. “Mixing was in the box, with the exception of the two tracks we mixed a year earlier, which we laid out over the SSL 9000, and the fact that we ran all sessions through a Studer A820 half‑inch, using Quantegy 499 Grand Master Gold half‑inch tape. I was absolutely mind‑blown by the enhanced sonics of using tape.

“Igor’s rough mixes were usually done with the two‑tracks of the beats, so when we started mixing, the first thing I asked for were the individual track‑outs of the beats. In general, whenever somebody sends me a two‑track with vocals, the first thing I request is the full tracked‑out instrumental. If they don’t have it, I respectfully decline the job. I don’t feel like that’s mixing, and I don’t feel I can do the song as much justice. And nowadays with Atmos mixes this issue is even more pressing. If you don’t have the tracked‑out beat, you’re going to have a problem with Atmos.

“I have strict preparation guidelines for people to stem out their multitrack for a final mix. I call it ‘stem out’, because I don’t need every element separate. There’s usually a lot of layering in the drums, with two or three or more kick drums, which I tell them to bounce out as one kick drum stem. If backing vocals are harmonies, just one stereo harmony group is OK. When sounds are layered, print them out as one sound. Keep the instrumental stems fully wet, keep the background vocals fully wet, and for the lead vocal, give me a tuned version that’s completely dry, and send me the effects returns separately.

“When people send me a full Pro Tools session to mix, I don’t want to work out why this track is going to that auxiliary, and then into another aux with maybe some strange EQ settings. I know my mind will wonder, ‘Why did they do it?’ Instead I prefer to receive everything committed, so when I load it in and press Play, it’s the same as the rough mix, and I can work from there. If there’s something technically wrong, I’m using my ears rather than my eyes to judge it.”

Back & Forth

A Love Letter To You 5 was therefore unusual in that Heldens was working not with stems but with Mamet’s Pro Tools sessions, which meant that he could see the treatments and signal chains in the session, particularly those that been used to treat the vocals. While he did load his template aux tracks into the sessions — “usually a Harmonizer, a standard hall reverb, plate reverb, half‑note delay, quarter‑note and eighth‑note delay” — he rarely used them.

“I moved tracks around in Igor’s sessions and colour‑coded things, so I knew visually where things were, and my eyes can easily lock on to what I’m hearing. We mixed nearly 30 tracks in total, and we would work on two or three songs a day, going back and forth so we wouldn’t get ear fatigue. Once we felt like we had a song at a certain level, where it’s not quite there yet but it’s solid enough, we’d switch our attention onto a next song, and we’d later return to these earlier songs. In some cases we restarted mixes from the ground up, because we didn’t feel they were on par with the rest of the songs.

“The rough mixes with the two‑tracks that Trippie had recorded to were our reference points, and sometimes it took time to recreate the beats exactly the way they were, because some of the processing had gotten lost in the stems that we received. After we loaded in the beat stems, I’d mute all the vocals, and I’d listen to whether there was a difference with the two‑track. Also, often producers only provided an eight‑bar loop originally, so we’d have to rearrange the beat according to whatever Igor had done. Once we had the session back to the rough mixes, the question was: ‘How can we make that better?’

“I kept whatever Igor had on Trippie’s vocals, process‑wise, but made small adjustments, usually just EQ, to make them sit better with the track. Many artists today have their own tracking engineer, who adds their own sound, and in this case, I preferred to just keep that. The only thing I might have done is add some EQ at the end if I feel there is some fine‑tuning to be done, just to make it fit better sonically. But in other mix situations I always add my own touch.”

Wind Breakdown

As an example of his mix work on A Love Letter to You 5, Heldens selects the song ‘Wind’, featuring the Kid Laroi. The beats, he says, required relatively little intervention. “The producers had picked really good kick and 808 samples that already had the right weight. Usually when an 808 misses some of the low end, I add either the Brainworx bx_subsynth or the Waves LoAir, just to synthesize sub. In this case the 808 was OK, and the kicks sat well with the 808. Usually I will do a side‑chain to duck whatever fundamental frequency the kick has on the 808 when they occur at the same time.

Waves’ Trans‑X Multiband was used to add some low‑end punch to the kick drum.Waves’ Trans‑X Multiband was used to add some low‑end punch to the kick drum.

“Because the kick was fine as it was, I did not need to apply the parallel compression chain I learned from Dave Pensado, but I did use it on the snare and clap tracks, with a ‘Snare Lift’ aux. Parallel compression is a great technique to accentuate frequencies on a source, and reinforce them, without changing the source sound sonically. When used on the kick, as I did on many other tracks on the album, I start with the Waves dbx 160 compressor, because it is very fast. I’m always knocking off 10dB of gain for a very snappy sound. I follow the dbx 160 with a Waves PuigTec EQP‑1A since it has very low phase shift. I add about 8‑9 dB at either 100Hz or 60Hz depending on what feels better. On the high band I roll everything off above 5kHz.

“I only used the Waves Trans‑X Multiband on the kick in the ‘Wind’ session. The snare/clap parallel in this session also starts with the dbx 160, but is followed by a Waves API 550A EQ, boosting 4dB at 200Hz (set to bell) and 1.5kHz, to get that in‑your‑face sound, and removing 2dB at 10kHz (set to shelf).

“All instruments are sent to the ‘INST’ aux, on which I have the iZotope Ozone 10 with the following modules: EQ adding some low end and taming a little of the high mids, Exciter to add some saturation, and Multiband compression to recreate the distinct pumping the demo reference had. I also added the Imager for some width and the Maximizer with a lot of soft‑clipping to recreate the demo’s lo‑fi sound. This is followed by FabFilter Pro‑L 2 to offload the heavy limiting between two limiters instead of one.

“Many of the beat tracks also have a send to the H3000 aux. It’s imitating the classic Eventide hardware Harmonizer from back in the day, where you slightly detune the left side, maybe flat, and the right side slightly sharp. I do it with the Waves Doubler and the Waves S1 Imager here. It makes the record a bit wider and creates more space for the lead vocal to sit solidly in the centre. I also usually send any of the ad libs and the background vocals to this.”


“When I apply parallel compression on lead vocals, as I did in some other tracks on the album, I use the Waves CLA‑76 Blue Face, because it distorts easily, which adds some nice texture to lead vocals. I set it to medium/slow attack and fastest release knocking off about 10dB gain. I follow this compressor up with the PuigTec EQP‑1A and add 4‑5dB at 100Hz and remove everything on the high band above about 5kHz. This chain lifts the lead vocal nicely out of the mix and to the forefront.

Inside Track

Trippie Redd’s vocals were often treated using a parallel path comprising a Waves CLA‑76 compressor and PuigTec EQ.Trippie Redd’s vocals were often treated using a parallel path comprising a Waves CLA‑76 compressor and PuigTec EQ.

“The Kid Laroi’s vocals were recorded in Melbourne. We originally received the dry vocal stems but felt when recreating the effects that we didn’t capture the same vibe and feel, so we requested the session from his recording engineer in Australia. We then flew Laroi’s vocals into our mix session with all his processing, automation and effects, as they were, apart from that we adjusted the EQ with the FabFilter Pro‑Q 3. The main plug‑ins used were the FabFilter Pro‑DS, Waves RComp, Waves SSL G‑channel, iZotope Neutron 4 Exciter, Waves DeEsser and Valhalla Vintage Verb.

“Igor created all of Trippie’s vocal effects, and I mostly left them the way they were. However, I removed some low end so it wouldn’t trigger the Waves CLA‑76 compressor, which is hitting between 3‑6 dB in gain reduction for some control. We also used the FabFilter Pro‑MB to dynamically control some of Trippie’s vocal’s boxy‑muddiness and some high‑end sizzle that was happening in the recording, and followed it up with some static EQ from the FabFilter Pro‑Q 3, removing some low thud and notching out some of his nasally tone. Igor added another compressor after that, the RVox. When coming back to mix I still felt Trippie sounded a bit harsh, and instead of going back in the previous processing I added the Waves C1 Side Chain to dynamically suppress some of that harshness.

Koen Heldens: With trap beats, they always put the closed hi‑hat dead centre and this occupies the same frequency space as the vocal. But if you pan it just to the left or the right, you will be surprised how much the vocal suddenly becomes more clear and more to the forefront.

“The hi‑hats and percussion in ‘Wind’ have the FabFilter Pro‑DS to tame some sharpness. With trap beats, they always put the closed hi‑hat dead centre and this occupies the same frequency space as the vocal. But if you pan it just to the left or the right, you will be surprised how much the vocal suddenly becomes more clear and more to the forefront. To achieve this I use a trick I learned from Dre, which is to mix for a moment in mono. I switch the monitoring to mono, while the session remains in stereo of course, and I can immediately hear whether something is clouding the vocal. If it is, I will literally pan it either just one step to the left or to the right, and you can immediately hear that the vocal becomes more clear.

“It’s one of these tricks that works, just like when you want to judge the level of the vocal versus that of the backing track. The traditional trick is to turn the monitoring level all the way down, until you can barely hear anything, and then you listen whether you can hear the entire song, or whether you hear only the instrumental or only the vocal. If it is only vocal, your vocals are too loud, if you hear only instrumental, your instrumental is too loud. You want to hear both.”

To Tape

“My template master bus chain consists of the Softube Bus Processor followed by the Chandler Limited Curve Bender, to add vibe and occasionally some high end. This is done within my Softube Console 1 system. It is followed by iZotope Ozone 10 using only two modules: EQ to roll off some low end, because the Curve Bender’s HPF is too broad; and I follow it with the Maximizer, knocking of about 2‑3 dB with True Peak enabled and a ceiling of ‑0.5dB.

“However, we took a different route for Trippie’s album. The only plug‑in we used was the Waves SSL G‑Master Bus Compressor, and we then ran the final mixes to tape. With some other mix sessions we also sent stems to the tape and then printed them back in the sessions, but for ‘Wind’ we only printed the final mix on tape, as hot as we could without distortion. We then recorded the mix from the tape to the studio’s computer in the room.

A Studer half‑inch tape machine at Criteria was used to print the master mixes for all tracks on the mixtape.A Studer half‑inch tape machine at Criteria was used to print the master mixes for all tracks on the mixtape.

Printing the mix to tape gave it a nice sheen. It wrapped the entire mix in some kind of nice soft blanket. It boosted the low mids, between 100 and 300 Hz, giving it a nice warm bump, and it added some harmonics. You can’t recreate this with a plug‑in or EQ.

“We mastered the entire album, loading everything into [Sonoris] DDP Creator, so that we could make sure that all the levels were cohesive between the songs, and that the transitions were the way that they envisioned them, and to be able to deliver vinyl A and B sides to the pressing plant.

“Interestingly enough, because you can’t run tape as hot as we nowadays do final masters, the whole album is mastered to ‑10 LUFS, because otherwise it would distort. It’s hip‑hop/R&B, so we can’t go as hot with the low end on tape. We considered adding another 3dB after we recorded back into the computer from tape, but it was really strange, it lost the magic of tape. So I was like, ‘Because of the more gentle nature of the music on the album, let’s not go with the loudness wars.’”

Koen Heldens

The first ever Inside Track article in Sound On Sound magazine featured Dave Pensado, who insisted on printing his email address. One of the people reading was a young dance music producer and engineer from the Netherlands called Koen Heldens. “I began emailing him,” remembers Heldens, “and after 20 emails or so, he responded. We developed a relationship and he showed me his parallel chains, which he had learned from Bob Powers. Somehow, they always work, and they are still at the heart of my mix approach. I also used them on the Trippie Redd album.

“The other big influence on my career was producer Dem Jointz, who worked in the same small studio facility in Los Angeles where I had set up. He was and still is signed to Aftermath Entertainment, the label of Dr Dre. I started mixing with Dem, and also with Focus... and the main thing that I learned from them was the importance of feel. I had become very technical in my approach, and they helped me to bring the feel back to my mixes, which is crucial, as music is all about emotion.”

Today, says Heldens, “I mix for the forest, not for the individual trees. So I barely solo anything. I listen to everything as a whole, because it’s a painting. I want to see the painting in full, and then if my ear catches something that is sticking out too much, I start homing in. I might solo that channel for a brief second to make sure that’s the sound and what the sound really represents. But in general there’s barely any soloing going on, and I’m almost always listening to the full track.

“I like to work in Logic, because of Softube Console 1. It is perfectly integrated with Logic, but not with Pro Tools. Whenever people see me working on that system, first they’re like ‘Why are you in Logic?’, and then they’re like ‘Oh I get it, because your sends are on faders, and your high cut and low cuts, and so on.’ It’s so intuitive. I feel like I have an instrument right in front of me, where I no longer depend on my visuals to see what’s happening, and can just use my ears. There’s also a way I do my gain staging with the Console 1 system. I know exactly the numbers of headroom I want to have.”

Working with reggae artist Sizzla on 2017 album I’m Yours led to Heldens meeting XXXTentacion and mixing his breakthrough singles, ‘Jocelyn Flores’ and ‘Fuck Love’ (featuring Trippie Redd) as well as the mega‑hit ‘Sad!’. The switch from EDM to hip‑hop/R&B involved an adjustment in his mixing techniques. “Both dance music and hip‑hop/R&B have many programmed elements, which are similar to work with. The main difference is in dealing with big low end, which Dave Pensado’s parallel chains were a real help with. XXX also liked to use heavy metal guitars, and to be honest, at the time I had no clue what I was doing. I would experiment and was purely going by what sounded cool to me, and I would send it to X to figure out whether he also thought it sounded cool.”

Koen Heldens spent part of the pandemic in Germany, where he mixed 30 top‑100 singles, including three number ones and three hit albums. Like many studio professionals, he moved to Miami in 2022, because there were no Covid restrictions in Florida. He’s since also mixed a lot of Latin music, and continued to work with Igor Mamut and Trippie Redd.