Comparison

Undersong vs Sound Terrain

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

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.

Highlights
  • 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
Read full description

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

About

Sound Terrain

Features
Read full description

Sound Terrain turns a field of colored cells into a small instrument. Tap to switch notes on and off, brush across the surface to strum, or hold to capture up to eight seconds of sound and release it across the terrain. Explore dust, wind, clicks, drones, bells and plucks. Spread two fingers to reshape a short tape loop. Draw an L for an echo, or trace a circle to leave a repeating phrase. Double-tap to mute a sound type. Your samples return as scattered grains, reverse playback and vocoder-like textures. Use rec to record a performance, then save or share the audio. Tilt your iPhone to send particles through the field, or enable camera brightness control to change speed and pitch by covering and uncovering the lens. Choose a palette or let colors follow the time of day. English and Chinese interfaces are included. Sound synthesis and recording work offline. No account, advertising or subscription. Microphone, camera and motion controls are optional. Samples are temporary and cleared by reset or closing the app process; exported performances remain wherever you save them. Playback pauses in the background.

Screenshots

Undersong4 screens
Sound Terrain4 screens

Verdict

The call

The clearest difference is price: Sound Terrain at $1.99 against Undersong's $9.99. Sound Terrain also leads on iOS requirement (15.0 vs 17.0). Undersong's advantage is update cadence (daily vs every 11 days). On ads, in-app purchases and device support 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

CostPrice · In-app purchases · Ads · Monetization

Undersong costs $9.99 and Sound Terrain $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Undersong ships an update daily, Sound Terrain every 11 days. The most recent releases landed on October 29, 2026 and October 24, 2026 respectively.

Scorecard3 real differences · 6 level
Undersong versus Sound Terrain: the parameters behind the verdict, then further details
ParameterUndersongSound Terrain
Price$9.99$1.99 — better
Rating5.0 (11 ratings) — better—
Number of ratings11 — better—
Update frequencyDaily — betterEvery 11 days
AdsNoNo
In-app purchasesNoNo
MonetizationPaid—
DevicesiPhone, iPadiPhone, iPod
Requires iOS17.015.0 — better
Further details — not scored
Size19 MB3 MB
Age rating4+4+
Developerian johnston弢 张

In-app purchases

None

Undersong

No in-app purchases

None

Sound Terrain

No in-app purchases

Questions

Is Undersong free?
Undersong costs $9.99, with no in-app purchases.
Is Sound Terrain free?
Sound Terrain costs $1.99, with no in-app purchases.
Do Undersong or Sound Terrain have ads?
Neither Undersong nor Sound Terrain shows ads.
Which is updated more often, Undersong or Sound Terrain?
Undersong ships an update daily, and Sound Terrain every 11 days. Most recently, Undersong was updated on October 29, 2026 and Sound Terrain on October 24, 2026.

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