Sightlines vs Undersong
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Sightlines
Shape sounds with a playable harmonic filter. Add motion, stereo spread, and unique textures to noise, samples, or synths. Tune it like a resonator or control it with MIDI for endless sonic possibilities.
- Harmonic filter bank
- MIDI control
- Sample loading
- Noise and synth sound sources
- Modulation capabilities
- Built-in chorus, delay, and reverb
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Make noise, texture, and percussion sing. Add motion and stereo spread to basic sounds. Load samples and sculpt them endlessly. Leave your mark on any sound with harmonic filtering. Sightlines is a playable harmonic filter. Built from a collection of resonant bandpass filters tuned to the harmonic series, designed to bring out a customizable set of musical frequencies in any sound. Tune it to a fixed frequency like a resonator, or send it MIDI to make it come alive as an instrument. Sightlines can be loaded as an instrument or an audio effect. As an instrument, use it with samples, noise, or oscillators to construct sounds never heard before. As an effect, add movement and interest to any sound, and even impart tonality onto unpitched input. SOUND SOURCES • Noise – filter variable color noise and random noise bursts for Sightlines’ simplest and quickest output. • Samples – send samples through resonant filters as one-shots or infinite looping versions of themselves, great for found sound and tonal samples alike. • Synth – skip the filters entirely and use Sightlines as a harmonic synth, where you can customize and modulate the proportion of each harmonic in the signal. • Audio effect – use Sightlines as an audio effect on any track. MOVEMENT AND EFFECTS • Manipulate overtones – stretch, bend, and reimagine the harmonic series to retune Sightlines’ output into realistic or indescribable sonic spaces. • Quantize frequencies – snap all of Sightlines’ filters to a scale, to impart that key quality onto any sound. • Balance bands – maneuver through the harmonic space by scanning, tilting, or spreading Sightlines’ bands. • End of chain – make your output shine with a built-in chorus, BBD-style delay, and reverb. FEATURES • Modulation – modify any control in Sightlines with multiple LFOs, sequencers, smooth random sources, and performance effects. • Presets – full preset control over every parameter in Sightlines. Cross-platform preset format for sharing with friends. • Waymaker – connect to Sightlines’ sibling application, Waymaker, for direct sequencing of Sightlines’ without MIDI routing. Also available for macOS and Windows in VST3 / AU / AAX formats from Aqeel Aadam Sound.
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
Screenshots
Verdict
The clearest difference is update cadence: Undersong at daily against Sightlines's weekly. Sightlines's advantage is price ($7.99 vs $9.99) and iOS requirement (13.0 vs 17.0). On rating, 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
Sightlines costs $7.99 and Undersong $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 5.0 for Sightlines against 5.0 for Undersong. Both are backed by a comparable volume of ratings — 9 and 11 respectively.
Sightlines ships an update weekly, Undersong daily. The most recent releases landed on October 24, 2026 and October 25, 2026 respectively.
| Parameter | Sightlines | Undersong |
|---|---|---|
| Price | $7.99 — better | $9.99 |
| Rating | 5.0 (9 ratings) | 5.0 (11 ratings) |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 9 | 11 — better |
| Update frequency | Weekly | Daily — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 13.0 — better | 17.0 |
| Further details — not scored | ||
| Size | 19 MB | 19 MB |
| Age rating | 4+ | 4+ |
| Developer | Aqeel Aadam | ian johnston |
In-app purchases
Sightlines
No in-app purchases
Undersong
No in-app purchases







