Callback Freeverb vs K.O. II
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Callback Freeverb
This app offers a classic algorithmic reverb effect based on the Freeverb algorithm. It adds depth, space, and atmosphere to audio sources, creating lush, spacious ambience. Designed for mono use, it provides a smooth, musical reverb tail suitable for vocals and synthesizers.
- Classic Freeverb algorithm
- Schroeder/Moorer reverb topology
- Comb and allpass filters
- Mono operation
- Adds depth and space to audio
- Smooth, musical reverb tail
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A classic algorithmic reverb effect based on the Freeverb algorithm by Jezar at Dreampoint. A Freeverb-style Schroeder/Moorer reverb based on the classic 8-comb + 4-allpass topology, with simplified controls and no stereo spread. This reverb creates lush, spacious ambience through a network of comb and allpass filters. Freeverb is widely used in electronic music production, ambient music, and sound design to add depth, space, and atmosphere to audio sources. The algorithm provides a smooth, musical reverb tail that works well on everything from vocals to synthesizers. This reverb only functions in mono and provides no stereo imaging, and the user can expect the same behavior as a classic Freeverb implementation otherwise.
K.O. II
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K.O. II is a compact native beat-making instrument for iPhone and iPad. Tap responsive pads, switch between drum, percussion, bass, and key banks, build 16-step patterns, and explore 38 included demo grooves. Designed as a focused standalone music surface, K.O. II gives you a hardware-inspired workflow for quick ideas, rhythm practice, and portable sound experiments.
Screenshots
Verdict
Callback Freeverb and K.O. II are too close to call on the numbers: across 5 compared parameters — price, ads, in-app purchases and device support among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
| Parameter | Callback Freeverb | K.O. II |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) — better | — |
| Number of ratings | 1 — better | — |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | — |
| Devices | iPhone, iPad | iPhone, iPad |
| Requires iOS | 17.0 | 16.0 — better |
| Further details — not scored | ||
| Size | 7 MB | 1 MB |
| Age rating | 4+ | 4+ |
| Developer | Callback Audio, LLC | 海洋 符 |
In-app purchases
Callback Freeverb
No in-app purchases
K.O. II
No in-app purchases







