Underground sits closer to Deep Horizen than it does to any of the other four Horizen expansion packs, and that’s exactly where this review lands: two packs fighting for the same dark shelf space, with Underground winning on immediacy and Deep Horizen winning on range. If you’re scoring something that needs to feel like a subway at 3am or a thriller chase cut, Underground is the right buy. If you want atmospheric flexibility, the competition has more ground to cover.
This expansion packs 47 presets into Tracktion’s Horizen synth, all built around haunting drones, gritty textures, and sinister movement. It’s built for film composers, ambient producers, and anyone who needs a dark emotional anchor in their signal chain without spending three hours on sound design. It is not for you if your idea of “dark” is a detuned pad with a low-pass filter.
How Does Underground Compare Out of the Box?
The comparison that comes up most in producer forums is Underground vs. Deep Horizen, the pack positioned as the ambient and atmospheric entry in the Horizen expansion lineup. Out of the box, the difference is immediate. Deep Horizen leans into slow-moving, spacious textures. Underground leans into tension. The drones feel tighter, more urban, and angrier.
Against third-party dark-cinematic libraries from developers like Output or Spitfire, Underground can’t match sheer content volume. But it earns its place through integration. Horizen’s layering engine means Underground presets are immediately stackable with your existing Horizen sounds, no bouncing to audio and importing files. That workflow advantage is real. It saves time every session.
Performance Deep Dive: What the 47 Presets Actually Deliver
We loaded Underground into a horror-adjacent project and ran through all 47 presets cold, no auditioning beforehand. About 30 of the 47 are genuinely usable in a cinematic context without touching a single knob. That’s a 64% straight-to-timeline hit rate, which is solid for a specialised pack at this price point.
The drones sit in a frequency range that feels like it’s been rolled off above 4kHz by default. Not a flaw. That’s a design choice that keeps them out of dialogue and lead melody space in a mix. The textures breathe at varying LFO rates depending on the preset, with some cycling slowly over 8 to 12 seconds and others staying almost static with barely perceptible movement. We found the static-feeling ones more useful under picture, because they don’t fight the edit rhythm.
We pulled up a specific preset we’re calling the anchor for this review: a low, sub-heavy drone that felt like it had harmonic content clustered around 80Hz and 160Hz. We ran it under a tense scene temp track. It sat. The film editor on the session didn’t ask us to move it. That’s the test.
One frustration: three or four presets in the pack feel like duplicate ideas with slightly different filter envelopes. At 47 total, you can’t afford redundancy. You wish those slots had gone to something rhythmic or a textural transition sound instead.
Where Underground Wins the Argument
The cleverness here is in the specificity. Tracktion didn’t try to make Underground do everything. They built 47 presets that do one thing well: dark, cinematic, tension-building sound design. For a composer on a deadline, that focus is satisfying. You don’t wade through 200 presets to find the 12 you’ll use. The useful ones are dense in the pack.
The intro price is great for what’s here. The Horizen base plugin has its own separate cost. If you’ve already made that investment, adding Underground at $30 is a no-brainer for anyone working in dark genres. The price-to-output ratio for film work, where a single well-placed drone texture can anchor an entire scene, tips comfortably in your favour.
The integration with Horizen’s own layering system is also a win. Loading an Underground preset and layering it under a melodic Horizen patch takes seconds. No export, no re-import, no format headaches.
Where the Competition Wins
Standalone WAV accessibility is the gap nobody in the marketing addresses, and it’s annoying. Producers who work across multiple DAWs, or who want to drag Underground textures into Ableton’s browser independently of the Horizen plugin, can’t do it. You’re locked to the ecosystem. Output’s Exhale or a Splice pack of dark textures doesn’t have that problem. You drag the file, you use the file.
The preset count is also a legitimate criticism. Forty-seven presets is a lean library when competing dark-cinematic packs often offer 100 to 200 sounds at similar or only slightly higher price points. Deep Horizen covers more emotional ground. If budget forces a choice between the two, Deep Horizen gives you more sonic flexibility over time.
The palette is also narrow by design, but that cuts both ways. If a project demands something slightly warmer or more ambiguous in tone, Underground’s presets resist that. There’s no gentle version of dark in here.
Who Should Buy Underground, and Who Should Skip It
✅ Buy if you score film, TV, or game audio and need a dark cinematic texture library that drops straight into a Horizen session without friction.
✅ Buy if you’re an ambient producer who works in the heavier, more industrial end of the genre and wants 47 pressure-tested starting points.
✅ Buy if you already own Horizen and want to expand the plugin’s sonic range toward tension and horror without spending more than $30.
❌ Skip if you don’t own Horizen. The pack is useless without it, and the base plugin changes the real cost of entry considerably.
❌ Skip if you want WAV-level access to your sounds for cross-DAW work. That’s not on offer here.
❌ Skip if you need a sonically diverse expansion. Underground is dark. That’s it.
Score Breakdown
| Category | Score | Notes |
|---|---|---|
| Sound Quality | 4.0/5 | Dark textures are well-designed and mix-ready; a few presets feel redundant |
| Value for Money | 4.0/5 | $30 for 47 cinematic-grade presets is fair if you already own Horizen. |
| Ease of Use | 4.5/5 | Horizen integration is frictionless; preset navigation is fast |
| Features | 3.0/5 | 47 presets is lean; no WAV access; palette is intentionally narrow |
| CPU Efficiency | 4.0/5 | Runs light within the Horizen engine on modern machines |
| Overall | 3.5/5 | A focused, well-executed dark cinematic pack held back by ecosystem lock-in and a thin preset count |
Alternatives to Consider
If Underground isn’t quite the right fit, here are three real options worth your time.
Deep Horizen (Tracktion): The ambient counterpart to Underground and the one we’d honestly recommend first if you’re torn. It covers more emotional ground and works as a better creative foundation if you score anything beyond pure-tension material. Deep Horizen expansion review
Output Exhale: A full dedicated vocal and texture instrument built for dark, cinematic, and experimental production. It’s more expensive, but the standalone format means no ecosystem lock-in, and the content depth is significantly greater. Output Exhale review
Akai MPC Expansion Underground Trap: Different animal entirely, but the name overlap causes genuine search confusion. If you’re after dark hip-hop and trap textures rather than cinematic drones, that’s the pack you want instead. We’ve covered it in full: MPC Expansion Underground Trap Review: Worth It in 2026
The Verdict on Underground
At intro pricing, Underground earns its place on any Horizen owner’s hard drive. The 47 presets are focused, dark, and mix-ready, and about 30 of them will land in your sessions with minimal editing. We’d buy this ourselves for horror and thriller scoring work.
But we’d be lying if we said the ecosystem lock-in doesn’t sting. If you want to drag a texture into Reaper or work outside Horizen’s wrapper, you can’t. That’s a real limitation for anyone who works across multiple setups.
Buy it at the intro price if you already own Horizen and score anything dark. At $30 regular price, it’s still defensible for film composers. If you don’t own Horizen yet, the real cost of entry is higher than this pack alone, and that changes the conversation entirely.
Frequently Asked Questions
Do I need to own Horizen to use the Underground Expansion Pack?
Yes, absolutely. Underground is an expansion pack for Tracktion's Horizen plugin, not a standalone instrument. It has no usable function without the Horizen base plugin installed and activated. The base plugin has its own cost, so factor that into your total if you're new to the platform.
How many presets are included in the Underground Expansion Pack?
Underground includes 47 presets, all built around dark, cinematic, and drone-heavy sound design. The pack is intentionally narrow in scope: don't expect melodic or bright-sounding patches in here. It's a tension-focused library from top to bottom.
Is the Underground Expansion Pack available in WAV format for use outside Horizen?
No. The expansion pack is locked to the Horizen plugin environment. There's no standalone WAV version of the sounds available, which is a genuine limitation for producers who work across multiple DAWs or want direct browser access to the audio files. If standalone format is important to your workflow, look at dedicated sample libraries instead.
What's the difference between Underground and the Deep Horizen expansion pack?
Underground is built specifically for dark, tension-heavy, and sinister sound design. Deep Horizen covers atmospheric and ambient territory with more emotional range. If you score across different tonal moods, Deep Horizen is the more versatile pick. If you need a dedicated dark cinematic tool and nothing else, Underground is sharper for that specific job.