Theremin I/O vs Chorus D
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Theremin I/O
Transform your iPhone into a touchless musical instrument using your camera and flash. Control sound generation by hand proximity, with options for scales, sound presets, and effects. An in-app purchase enables MIDI controller functionality.
- Touchless instrument control via camera
- Adjustable scales and harmony quantization
- Multiple sound presets with effects
- MIDI controller functionality (in-app purchase)
- Interactive tutorial overlay
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Play with light – Theremin I/O turns your iPhone into a touchless music instrument. It uses your camera and flash to measure the distance to your hand, this signal is then processed by a synthesizer to generate a tone. Features: • Old-school synthesizer • Constrain input to scales (harmony quantization) • 8 sound presets with effect controls • 50+ scale presets • Use as a MIDI controller (requires in-app purchase) • Learn fast with the tutorial overlay For more information visit http://theremin.io
Chorus D
This audio unit effect emulates a classic chorus stomp-box with a unique, subtle sound. It offers a wider stereo image and thicker sound without the typical pitch-wavy artifacts. Its simplified interface provides a range of tasteful tones.
- Subtle stereo pitch-shifting
- Constant pitch-shift amounts
- Stereo image widening
- Sound thickening
- Six tasteful presets
- Unique sound profile
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Chorus D is an audio unit effect inspired by a well-loved classic chorus stomp-box. HOW IS IT DIFFERENT FROM OTHER CHORUS EFFECTS? It's more subtle. It has a stereo pair of pitch-shifters, one shifts up and the other down. Every few seconds, the two pitch shifters trade places: the high one goes low and the low one goes high. Unlike most other chorus effects, the pitch-shift amounts stay constant rather than oscillating up and down. For that reason, you don't hear the wavy pitch sound that other chorus effects make. At low settings, you can put it on a track to widen the stereo image or thicken up the sound and listeners may not be able to identify that they are hearing a chorus effect. WHY ONLY SIX BUTTONS? The original hardware that inspired this design had only four buttons and four presets, one for each button.* The simplicity of the controls is one of the reasons the effect was so well-liked: all four presets sounded great. With six buttons you get tones ranging from very subtle to clearly audible, and all of them are tasteful and useful. This effect makes only one type of sound but it's a unique sound that you don't get from other chorus effects. IS THIS AN EXACT CIRCUIT MODEL OF THE ORIGINAL HARDWARE EFFECT? No. We listened to the original and studied its design but then we built an effect to please our own ears. It sounds similar to the original but the design is unique. ************************************ Note: this is an audio unit plugin. It does not process audio as a standalone app. *Later on customers figured out that they could get some other settings by pressing two buttons simultaneously or forcing all the buttons off. We are using six buttons to get wider variety of sounds rather than expecting customers to discover those secret features of the original hardware.
Screenshots
Verdict
The clearest difference is rating: Chorus D at 5.0 against Theremin I/O's 4.0. Chorus D also leads on in-app purchases (none vs 1) and review sentiment (100% vs 77%). Theremin I/O's advantage is price ($2.99 vs $5.99) and chart position (#187 vs unranked). On ratings volume, ads, monetization model 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
Theremin I/O costs $2.99 and Chorus D $5.99 up front. Theremin I/O sells 1 one-off in-app purchase. Chorus D asks for nothing beyond the download.
Chorus D holds the better App Store score, 5.0 against 4.0. Both are backed by a comparable volume of ratings — 5 and 6 respectively. Written reviews point the same way: 77% of Theremin I/O's written reviews are positive against 100% of Chorus D's.
Theremin I/O ships an update every 24 months, Chorus D every 7 months. Both last shipped on October 12, 2026.
| Parameter | Theremin I/O | Chorus D |
|---|---|---|
| Price | $2.99 — better | $5.99 |
| Rating | 4.0 (5 ratings) | 5.0 (6 ratings) — better |
| Positive reviews | 76.9% of reviews | 100.0% of reviews — better |
| Number of ratings | 5 | 6 — better |
| Update frequency | Every 24 months | Every 7 months — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Paid | Paid |
| Best chart rank | #187 — better | — |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 8.0 — better | 12.0 |
| Further details — not scored | ||
| Size | 18 MB | 11 MB |
| Age rating | +4 | 4+ |
| Developer | FFFF00 Agents AB | Blue Mangoo Consulting Company Limited |
Customer experience
Theremin I/O
Chorus D
In-app purchases
Theremin I/O
- Network MIDI$5.99
Chorus D
No in-app purchases









