Undersong vs FIELD KIT Playback Engine
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Undersong
This audio effect acts like an instrument, generating synthesized notes in key based on incoming audio. Explore a vast array of sound combinations with various materials, modes, and patterns for unique ambient performances.
- Generates in-key synthesized notes from audio input
- 12 material types and 10 performance modes
- 10 pattern options for sound shaping
- Self-generating ambient pad mode
- Gravity feature for melodic anchoring
- Customizable scales and root notes
- Integrated reverb effect
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Undersong is an AUv3 audio effect that plays along with whatever audio you send it. It's technically an audio effect, but it acts more like an instrument. It's based on an idea I had for a live performance that ended up taking on a life of its own. The short version is that everything Undersong plays comes from the audio coming in. It listens to your track for "action", like a pluck, a drum hit or a swell, and each of those can spawn a particle. A particle is one small synthesized note, often a pluck but not always, and it's always in key. Soft playing gets soft and lower responses, and digging in gets you brighter ones. I feel like Undersong is something that wishes to be the main focus of a composition, but how you use it is totally up to you. I really enjoy using it as the centerpiece of ambient jams with a bit of percussion or a slow moving bassline alongside. If you're not sure where to start, send in a drum loop (even just a series of blips or clicks will work...), turn up the Mix to 100% and just experiment for a while. Twist some knobs and see what you find. You can't break it. The particles can be one of 12 materials, mostly inspired by modular synthesis techniques. Each material can then be performed and shaped by one of 10 modes and 10 patterns. That makes for 1200 combinations before you turn a single dial. One of the modes, Aurora, stops making particles altogether and turns into a self-generating ambient pad that your playing strikes. It's one of my favorite things in the device. I tried to build this like a playground for ambient performances. It's maybe a bit like sitting down at someone else's modular rig... it takes some exploration. I've set up an environment that I think is inspiring and I hope you can find your way around and enjoy it as well. There's various ideas and features hidden throughout (in plain sight) that work nicely together or on their own. Gravity, an idea I brought over from my Augur device, pulls the notes toward your root so the melodies sound like they're actually in your key. With Ear on, Undersong listens for the pitch you're playing and answers in unison, grain plays tiny pieces of your own audio back as notes, and Input lets little glimpses of your audio through, so you hear the thwack of your pick or your snare, but ringing at the particle's note. Step puts everything on a steady rhythm, one note per step, with Density deciding how busy it is. Step plus the Loop pattern is a fun little corner to jam in. Freeze holds whatever's currently ringing out so you can play over it. There's a Drone dial that builds a bed under everything, and 35 scales plus your own custom ones. Plus a quick one-knob reverb, because I really like reverb and I think almost every one of my devices has received at least a little reverb, just in case you need it quickly. To sum up, I'm proud of this and I have been consistently getting lost in it while building and testing. I feel it's the kind of device that you have to get to know a bit. It's pretty dense. It's maybe not for everyone, but for the people who it resonates with, I'm glad you're here and I hope it brings you some inspiration. If you run into any issues or have some feature requests for a later update, don't hesitate to reach out at ian@ijoaudio.com. I appreciate you very much. Cheers! ian - ijo audio
FIELD KIT Playback Engine
Transform audio recordings into evolving textures, rhythms, and atmospheres. Create up to four independent playback windows with customizable speed, direction, and effects. Explore new sonic material from your recordings.
- Up to four independent playback windows
- Variable playback speed and direction
- Drive and filtering per window
- Routable modulation sources
- Save and recall .fieldkit files
- Standalone app and AUv3 Audio Unit
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FIELD KIT is an audio playback instrument built for turning recorded sound into evolving texture, rhythm, and atmosphere. Load an audio file and create up to four independent playback windows across the recording. Each window can move through a different section of the source with its own playback speed, direction, crossfade, drive, filtering, level, and pan. Use FIELD KIT to pull overlapping textures from long field recordings, transform environmental sound into ambient beds, create asynchronous loops, or find entirely new material hidden inside a recording. Three modulation sources can be routed independently across the playback windows, allowing parameters to drift, pulse, and evolve over time. Features include: - Up to four independent playback windows - Forward, reverse, and ping-pong playback - Variable playback speed - Adjustable loop crossfade - Drive and filtering per window - Independent level and pan controls - Three routable modulation sources - SPLICE for working with multiple audio sources - Save and recall .fieldkit files to share across platforms - Internal recording in Standalone mode - Standalone app and AUv3 Audio Unit - Host transport support in compatible AUv3 hosts FIELD KIT was designed around a simple idea: a recording doesn't have to be played from beginning to end. It can be a place to explore.
Screenshots
Verdict
The clearest difference is update cadence: Undersong at daily against FIELD KIT Playback Engine's every 2 weeks. Undersong also leads on rating (5.0 vs 4.6). FIELD KIT Playback Engine's advantage is iOS requirement (15.0 vs 17.0). On price, ratings volume, ads and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Undersong costs $9.99 and FIELD KIT Playback Engine $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.
Undersong holds the better App Store score, 5.0 against 4.6. Both are backed by a comparable volume of ratings — 11 and 5 respectively.
Undersong ships an update daily, FIELD KIT Playback Engine every 2 weeks. The most recent releases landed on October 25, 2026 and October 26, 2026 respectively.
| Parameter | Undersong | FIELD KIT Playback Engine |
|---|---|---|
| Price | $9.99 | $9.99 |
| Rating | 5.0 (11 ratings) — better | 4.6 (5 ratings) |
| Positive reviews | — | 80.0% of reviews |
| Number of ratings | 11 — better | 5 |
| Update frequency | Daily — better | Every 2 weeks |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Best chart rank | #192 | #143 — better |
| Devices | iPhone, iPad | iPhone, iPad, iPod — better |
| Requires iOS | 17.0 | 15.0 — better |
| Further details — not scored | ||
| Size | 19 MB | 12 MB |
| Age rating | 4+ | 4+ |
| Developer | ian johnston | Field Tone Audio, LLC |
In-app purchases
Undersong
No in-app purchases
FIELD KIT Playback Engine
No in-app purchases
Questions
Is Undersong free?
Is FIELD KIT Playback Engine free?
Which has better reviews, Undersong or FIELD KIT Playback Engine?
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