Comparison

FormKey vs In Theory

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

Head to head
About

FormKey

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
Read full description

Unlock your music potential. FormKey is the first music suite that helps you become the musician you've always imagined being, just by using it. INTRODUCING FORM Form is a new way to read and create music. Notes become shapes. Octaves become colors. Duration becomes a simple to read fraction. You can learn to read and play music in minutes. FormKey is the first release of the Form notation language, an open licensed music language designed to create instant music literacy. With the goal being to become a standard you'll see everywhere. THREE MODES: CREATE, LEARN, AND CONTROL • Create mode gives you a 16-track sequencer built on the classic drum machine workflow, modernized for today. Use your own AUv3 plugins or the three we built in to create full tracks from the ground up. • Learn lets you play and read your way through classical pieces while Form teaches you exactly what the music is doing, note by note. • Control turns FormKey into a MIDI controller for your external workflows, so it fits right into the setup you already have. THREE BRAND NEW AUv3 PLUGINS • Tone is a fully interactive subtractive synth that makes synthesis make sense. Every knob and connection is something you can hear and understand, so the architecture of a sound stops being a mystery. • Wave is a file-based sampler that lets you chop audio samples from your device, designed to make Slicing, and rearranging samples feel effortless instead of technical. • Patt3rn is a suite of modeled instruments curated to provide users with high quality options when looking for go to sounds every sequencer needs. • All 3 work in any host, so the instruments you learn in FormKey come with you wherever you go. SCALE MODE Reshape the keyboard to any of 26 scales, so every note you play stays in key. Choose from: • Major and minor: Major, Natural Minor, Melodic Minor, Harmonic Minor • Modes: Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, Locrian • Pentatonic and blues: Major Pentatonic, Minor Pentatonic, Blues • Symmetric: Whole Tone, Whole-Half Diminished, Half-Whole Diminished, Augmented Hexatonic • World and exotic: Hungarian Minor, Neapolitan Minor, Byzantine, Enigmatic, Hirajoshi, In Sen, Kumoi, Iwato We've refined the interface across the app, making FormKey easier and more enjoyable to use. Every feature in FormKey is free to try. In celebration of our launch, $14.99 unlocks everything for the life of the app. We hope you love it as much as we do.

About

In Theory

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
Read full description

In Theory is an interval based MIDI keyboard app with more than 110 scales. It has a keypad at the bottom with the interval buttons like +2, +1, 0, -1, -2 which would change the current note. Zero means the current note, +1 means the note after the current note, +2 means two notes after the current note, -2 means two notes before the current note in the scale and so on. Above the keypad, you can toggle additional intervals in the scale for creating chord voices. You can also select the notes from an octave above and an octave below for creating rich, extended chords. You can use your MIDI keyboard to play In Theory as well. The middle C4 key on your MIDI keyboard triggers the 0 (zero) button on the app's keypad. The white notes after the C4 note would trigger the positive buttons, the white notes before the C4 note would trigger the negative notes on the keypad. You can also toggle the chord intervals with MIDI CC messages. You can set a MIDI CC number and a MIDI Channel for toggling the chord intervals from the settings menu. If you send a MIDI CC value between 0-62, you can toggle the chord intervals respectively. With the MIDI capabilities, you can also sequence the app with a MIDI sequencer app like PolyBud, ShiftBud, MelodyBud etc. In Theory has more than 110 scales built-in. You can also use the custom scales you made in ScaleBud 2 app as well. The key and scale could be changed externally from a MIDI controller in AUv3 plugin with the AU parameters. The circular display on the UI will show you where you are in the scale. Also, when you play a note, you will see the every playing note on the screen with the root note and the chord intervals. Please note that In Theory is a MIDI app and does not produce any kind of sound on its own. You need to connect the MIDI output of the app to an audio app's MIDI input. For the AUv3 plugin you'll need an AUv3 host app such as AUM, Cubase, Nanostudio, apeMatrix etc.

Screenshots

In Theory4 screens

Verdict

The call

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.

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

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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

Scorecard6 real differences · 4 level
FormKey versus In Theory: the parameters behind the verdict, then further details
ParameterFormKeyIn Theory
PriceFree — better$4.99
Rating4.5 (8 ratings)5.0 (4 ratings) — better
Positive reviews57.1% of reviews100.0% of reviews — better
Number of ratings8 — better4
Update frequencyFortnightlyWeekly — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationPaidPaid
DevicesiPadiPhone, iPad, iPod — better
Requires iOS18.613.0 — better
Further details — not scored
Size88 MB7 MB
Age rating4+4+
DeveloperPolyhedraCem Olcay

Customer experience

FormKey

All ratings8 ratings
Positive75.0%
Neutral25.0%
Negative0.0%
Written reviews7 reviews
Positive57.1%
Neutral28.6%
Negative14.3%

In Theory

All ratings4 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews2 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

1 purchases

FormKey

One-time1
  • FormKey Full Unlock$14.99
None

In Theory

No in-app purchases

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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