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Keepforest – Ferrum (Review)

keepforest ferrum review

Keepforest is back with a new, hard-hitting sample library: Ferrum – Modern Trailer Percussion. As the caption suggests, Ferrum is a massive percussion instrument geared towards trailer music and cinematic music production. It offers a large collection of highly processed cinematic percussion that ranges from epic trailer hits and ensemble drums to various metals, cymbals, foley percussion, and more.

I had the chance to check out Ferrum recently and in this review, how the library works, and what it sounds like.


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Ferrum is a sample library for Native Instruments’ software sampler Kontakt version 6.0.2 and above. It’s compatible with both the free Kontakt Player as well as with the paid Kontakt sampler. Ferrum is roughly 8.5 GB in size and includes the Kontakt sample library as well as an additional “WAV Folder” containing all of the library’s samples as audio one-shots. It’s completely up to you if you want to use Ferrum’s cool user interface and play the samples with your keyboard or if you prefer to just drag and drop the sound files right into your project.

Ferrum comes with 550 sounds structured into 23 different patches in total which feature various ensemble drums, trailer hits, and auxiliary percussion.

Keepforest also offers a Free Edition of Ferrum featuring a handpicked selection of the percussive sounds in the full version. You can check out and download the free version of Ferrum via Keepforest’s new online store.


The Belarus-based developers at Keepforest are well-known in the trailer music industry for providing composers with massive, state-of-the-art trailer sound design and percussive effects. With Ferrum (the Latin word for iron), Keepforest focused on cutting-edge, high-energy percussion centered around metallic sound sources. These include massive drum ensembles with a metallic edge, industrial percussion, anvil strikes, as well as various cymbals, bells, and a huge collection of small to mid-sized metal clanks and hits.

A major innovation that is introduced with Ferrum, is that for the first time, all these percussive elements are presented in a truly playable fashion. This means that most of the drum sounds were captured with various round-robin variations (up to 16!) that allow for a much more realistic playing experience without the dreaded “machine gun effect”. While round robins are pretty much standard for conventional or orchestral percussion sample libraries, having highly-processed trailer hits that vary slightly every time you hit the keyboard is definitely something new.


For Ferrum, the developers at Keepforest came up with a fresh and unique UI concept that is perfectly tailored to the application of the library. The interface makes a sleek and clear first impression and has its various functions neatly structured into three control tabs.

Mic Balance Control

On the Main tab, the Mic Balance Control on the left lets you choose between different microphone positions for your sound. You can use these mic mixes to make the overall sound of your patch either more punchy and direct or to give it a more set-back, roomier feel. The microphone options vary depending on the patch. Most patches provide a close and a room mix or feature a reverb instead of the room mix. One single patch, the Factory Hall Ensemble even offers a selection of 4 unique microphone positions including a close, mid, far, and a room position.

On the patches that feature a dedicated reverb fader, you can change the type of room sound you want by choosing between one of the 13 available reverb styles. These are based on Kontakt’s stock library of reverb impulse responses.

The Stage

Using the microphone icon found on the virtual stage in the GUI’s center, you can quickly adjust how close or roomy you want your drums to sound. By moving the icon around, you can see how the Mic Balance Control on the left automatically adjusts their fader positions to represent the microphone’s position on stage. The Stage also allows you to quickly change the panning, either globally or on a per-sound basis. Both features make the Stage a really useful visual representation of your final sound.

keepforest ferrum main interface
Ferrum – Main User Interface

Round Robin Control

Directly below the Stage area, you can see how many round-robin variations a particular sample has to offer. This is displayed by the number of gold-framed squares in the matrix. The number changes depending on which sample you trigger on the keyboard and ranges from a few variations to up to 16 individual round-robins.

Playback Mode

The Playback Mode in the upper right corner lets you choose different options of how the samples are triggered. While Mono and Stereo playback is pretty self-explanatory, the Doubling and Ensemble modes are quite interesting. Doubling takes the same sound and automatically pans one round-robin hard left and another one hard right. This gives you a super-wide stereo experience that can be understood as a hyped version of the Stereo playback. The Ensemble mode takes this up a notch by simulating an ensemble of up to 16 players hitting the same drum. This is done by triggering multiple round-robins of a sample at once while introducing slight timing variations. Depending on the number of virtual players selected, you can create huge walls of sound. However, increasing the number of players also washes out the punchy transient portion of a drum sample, thus making it sound softer and less snappy. Although the Ensemble mode is a very cool feature, it’s best used in moderation if you’re trying to maintain a punchy sound.

Velocity Curve

The user interface of Ferrum also provides an option to adjust the velocity curve of the incoming MIDI signal. This allows you to adjust the behavior of the dynamic playback to your playing style. If you select a Brickwall setting, for example, it makes any incoming MIDI velocity values the same. No matter how soft or hard you play the keyboard, you’re always triggering all samples at the exact same loudness. In contrast, the Scale Curve setting only triggers soft to medium velocities, even when you’re hitting your keyboard with full force. Depending on what you’re trying to accomplish, the Velocity Curve control can help you to have an easier time performing the rhythmic lines you have in mind.

Envelope Section

The AHDSR section on the bottom right lets you tailor the envelope of the drum sounds to your liking. Make everything snappier and shorter by dialing down the Decay and Release or reduce the transient portion of a sound and create a softer, swell-like sound by turning up the Attack control. These adjustments can be made both globally or for each individual sample if you like to.


Ferrum features an elaborate step sequencing section accessible through the Rhythm tab at the lower right side of the UI. The Rhythm tab features a huge selection of pre-programmed rhythms ranging from basic repetitions to complex, cinematic action patterns. These rhythms aren’t recorded as audio loops but are created on the fly using MIDI. This enables you to use the collection of programmed rhythms with any sample of Ferrum. It’s of course perfectly possible to create your very own percussive lines entirely from scratch. If you ever used a step sequencer to dial in rhythmic sequences on a synthesizer, you should feel at home pretty quickly.

Keepforest Ferrum Rhythm Sequencer
Ferrum – Rhythm Sequencer

Not only do you have control over the loudness and length of each drum hit in a sequence, but you can also program the panning, filter settings, and pitch of each hit. This makes the Rhythm engine a perfect tool for coming up with unique rhythmic sequences.


Just like most other Keepforest products do, Ferrum features its own master effects section. Accessible through the Master tab, this section provides you with a chain of 7 freely assignable stock Kontakt effects that affect the whole patch. For each FX slot, you have the choice between any of Kontakt’s 25 stock effects. These range from various dynamic processors, EQ, saturation, and distortion, to modulation effects, delay, reverb, and even more. The fact that you can freely assign and move around all the FX slots allows for very elaborate creative options that sound designers will love.

Ferrum master effects
Ferrum – Master Effects Slots


Ferrum has a hyped and massively processed sound across most of its percussive instruments, which makes it a perfect fit for hard-hitting trailer music and action scoring. Most patches feature a “Smiley Face” frequency curve, in which the mids are scooped out and the bass and treble frequencies are boosted to help cut through even the densest mixes.

A unique feature of the sample library is that Ferrum offers multiple round robins for each trailer drum sound, which allows you to play quick repetitions without the rhythm becoming too machine-like. Not all round robins are completely unique though, which sometimes becomes apparent when hitting two keys of the same sound category at once. When doing so, you occasionally trigger a phasing effect or samples that stick out by becoming twice as loud. This is probably due to the sound design team taking the same drum sound as a base and creating the round robins with variations of the high-frequency content.

Each percussion patch features a range of different drum sounds spread across multiple octaves. For some of the patches, the sound gets wider the higher your go up on your keyboard. This provides you with a lot of options to vary the depth and width of the drum sound according to your arrangement.

Apart from the great-sounding epic trailer hits, short punches, and huge one-shot impact sounds, Ferrum offers a comprehensive collection of struck metals, rods, and foley sounds in different shapes and sizes. These offer a great addition to the big hits since you can use them to fill out your deep percussion lines with fast, metallic, tick-tock-y rhythms. The Various Metals category alone features 9!! individual patches filled with small to tiny metal percussion hits. Although they all sound very clean and punchy, they are quite similar in tone and thus throw off the balance of the sample library a bit. Instead of having so many metallic click-and-clack sounds to choose from, I would have rather wished for even more ensemble hits, a couple of cool transition sounds, or cymbal swells for example.


Ferrum offers everything you need in terms of hard-hitting, state-of-the-art trailer percussion. Although the sample library is certainly geared towards a specific field of trailer music, you will find a huge selection of awesome sounds and options to choose from. Ferrum’s user interface is one of the library’s absolute highlights and probably one of the best Keepforest came up with so far. It offers great flexibility and easy control over the tone, width, and depth of the samples. The generous amount of round robins for each drum sound makes programming fast rhythmic lines a joy, even though not all of them are created entirely from scratch.

The price point of this rather specialized sample library surely makes it more attractive for professionals than for hobby composers. If you’re looking to spice up your hybrid and sound design trailer cues with massive, powerful, and processed percussion though, Ferrum is definitely one of the best options out there at the moment.


  • Massive, stylized trailer percussion
  • Great variety of drums and metals
  • Many round robins
  • Excellent user interface
  • Sequencer & built-in FX offer many customization options
  • Works with the free version of Kontakt


  • Many similar-sounding metallic patches
  • Not all round-robins are uniquely recorded



Ferrum is available as a digital download through Keepforest’s online store for $299. Keepforest also offers a free trial version of Ferrum that features a hand-picked selection of the sounds found in the full library.



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