# FormKey vs In Theory

The clearest difference is price: FormKey at Free against In Theory's $4.99. In Theory's advantage is review sentiment (100% vs 57%) and rating (5.0 vs 4.5). On ratings volume, update cadence, ads and monetization model there is nothing between them.

FormKey is free to download; In Theory costs $4.99 up front. FormKey sells 1 one-off in-app purchase. In Theory asks for nothing beyond the download.

In Theory holds the better App Store score, 5.0 against 4.5. Both are backed by a comparable volume of ratings — 8 and 4 respectively. Written reviews point the same way: 57% of FormKey's written reviews are positive against 100% of In Theory's.

FormKey ships an update fortnightly, In Theory weekly. Both last shipped on November 3, 2026.

## The numbers

| Metric | FormKey | In Theory |
| --- | --- | --- |
| Price | **Free** | $4.99 |
| Rating | [4.5 (8 ratings)](https://appshunter.io/ios/app/formkey/id1535350561/reviews) | **[5.0 (4 ratings)](https://appshunter.io/ios/app/in-theory-interval-keyboard/id1667984658/reviews)** |
| Number of ratings | **8** | 4 |
| Positive reviews | 57.1% of reviews | **100.0% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Fortnightly | **Weekly** |
| Monetization | Paid | Paid |
| Size | 88 MB | 7 MB |
| Requires iOS | 18.6 | **13.0** |
| Devices | iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Polyhedra](https://appshunter.io/developer/1535350563) | [Cem Olcay](https://appshunter.io/developer/523633853) |

## What reviewers say

### FormKey

[App page](https://appshunter.io/ios/app/formkey/id1535350561)

This app is an intuitive MIDI controller that helps musicians improve by using shapes for notes and colors for octaves. Its unique isomorphic keys aid in pattern recognition and chord discovery, making music creation more accessible.

**Highlights:** Shape-based note input, Color-coded octaves, Isomorphic key layout, Pattern recognition aid, Chord discovery assistance, Future update commitment

**Features:** Family Sharing, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| FormKey Full Unlock | $14.99 | one-time |


### In Theory

[App page](https://appshunter.io/ios/app/in-theory-interval-keyboard/id1667984658)

This app provides a unique interval-based MIDI keyboard with over 110 scales. It allows for flexible chord creation by toggling additional intervals and notes from different octaves. It integrates with external MIDI keyboards and sequencers for advanced music production.

**Highlights:** Interval-based MIDI keyboard, Over 110 built-in scales, Customizable chord voicing, MIDI keyboard input support, MIDI CC message control, AUv3 plugin compatibility, Visual scale and note display

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

**In-app purchases:** none


## Frequently asked questions

### Is FormKey free?

FormKey is free to download, with in-app purchases available.

### Is In Theory free?

In Theory costs $4.99, with no in-app purchases.

### Which has better reviews, FormKey or In Theory?

In Theory is rated higher. FormKey averages 4.5 out of 5 from 8 ratings, while In Theory averages 5.0 from 4 ratings.

### Do FormKey or In Theory have ads?

Neither FormKey nor In Theory shows ads.

### Which is updated more often, FormKey or In Theory?

FormKey ships an update fortnightly, and In Theory weekly. Most recently, FormKey was updated on November 3, 2026 and In Theory on November 3, 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.*