# Theremin I/O vs Index Theremin

The clearest difference is price: Index Theremin at Free against Theremin I/O's $2.99. Index Theremin also leads on in-app purchases (none vs 1) and update cadence (every 3 weeks vs every 24 months). Theremin I/O's advantage is iOS requirement (8.0 vs 17.0). On ads and device support there is nothing between them.

Index Theremin is free to download; Theremin I/O costs $2.99 up front. Theremin I/O sells 1 one-off in-app purchase. Index Theremin asks for nothing beyond the download.

Theremin I/O ships an update every 24 months, Index Theremin every 3 weeks. Both last shipped on November 6, 2026.

## The numbers

| Metric | Theremin I/O | Index Theremin |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | **[4.0 (5 ratings)](https://appshunter.io/ios/app/theremin-io/id669456913/reviews)** | — |
| Number of ratings | **5** | — |
| Positive reviews | 76.9% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 24 months | **Every 3 weeks** |
| Monetization | Paid | — |
| Size | 18 MB | 1 MB |
| Requires iOS | **8.0** | 17.0 |
| Devices | iPhone, iPod | iPhone, iPad |
| Age rating | +4 | 4+ |
| Developer | [FFFF00 Agents AB](https://appshunter.io/developer/288966262) | [NOAH REMI FINN BESENDORFER STAHLHACKE](https://appshunter.io/developer/1836253254) |

## What reviewers say

### Theremin I/O

[App page](https://appshunter.io/ios/app/theremin-io/id669456913)

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.

**Highlights:** Touchless instrument control via camera, Adjustable scales and harmony quantization, Multiple sound presets with effects, MIDI controller functionality (in-app purchase), Interactive tutorial overlay

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Network MIDI | $5.99 | one-time |


### Index Theremin

[App page](https://appshunter.io/ios/app/index-theremin/id6818808236)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Theremin I/O free?

Theremin I/O costs $2.99, and also offers in-app purchases.

### Is Index Theremin free?

Index Theremin is free to download, with no in-app purchases.

### Do Theremin I/O or Index Theremin have ads?

Neither Theremin I/O nor Index Theremin shows ads.

### Which is updated more often, Theremin I/O or Index Theremin?

Theremin I/O ships an update every 24 months, and Index Theremin every 3 weeks. Most recently, Theremin I/O was updated on November 6, 2026 and Index Theremin on November 6, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*