# 24-TET Keys: Microtonal MIDI — Quarter Tones on a Keyboard > Microtonal MIDI keyboard app for exploring quarter tones and unusual tunings. (iPhone/iPad app by Maxim Oransky.) - Source: https://appshunter.io/ios/app/24-tet-keys-microtonal-midi/id6789963675 (this page in markdown: same URL + `.md`) - Developer: [Maxim Oransky](https://appshunter.io/developer/1639941241) - Category: Music, Productivity - Price: Free - Rating: 4.60/5 from 5 App Store ratings · 3 written reviews indexed - Age rating: 4+ - Requires: iOS 17.6 · 4 MB - Languages: American English - Released: 2026-07-14 - Data updated: 2026-09-08 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/24-tet-keys-microtonal-midi/id6789963675/reviews.md ## What is 24? Quarter tones on a keyboard you already know. 24-TET Keys is a microtonal keyboard for iPhone and iPad: play the notes between the notes with your fingers, hear them as you press them, and send them on as MIDI if you have somewhere to send them. CAN YOU PLAY QUARTER TONES ON A PIANO? Not on an ordinary one, which is why quarter-tone pianos are rare instruments in a handful of cities. Here the piano board is the starting point. Naturals sit in a row, sharps ride above them, and the quarter tones grow into the gaps with an animated morph, so you can watch 24-TET come out of the notes you already play. Charles Ives wrote his Three Quarter-Tone Pieces for two pianos tuned a quarter tone apart. WHAT DOES A QUARTER TONE SOUND LIKE? Press one. It makes sound out of the box, so you hear the interval instead of reading about it: polyphonic, played by touch, with glissando slides straight across the quarter tones. A quarter tone is half a semitone, 50 cents, the gap between two piano keys cut in two. MICROTONAL CHORDS, NOT JUST SCALES Every finger is its own voice, so a neutral third holds its pitch inside a chord instead of dragging the other notes with it. That is the part quarter tones usually break. LAYOUTS THAT MORPH INTO EACH OTHER This is an experimental collection of unusual keyboard layouts, and not a menu of separate boards: each is a point in one space, and any of them morphs into any other while you watch. The piano-derived board is one point. So is a domino board, where a key carries its natural below and its quarter tone above. So is a snake through the honeycomb. So is an isomorphic layout, where a chord shape is the same shape in every key, the property that makes hex boards worth learning. You can morph out of the piano you know straight into the honeycomb, the bridge between the two. MICROTONAL MIDI KEYBOARD: SEND IT TO A DAW If you already make music and want quarter tones in it, this is the compact microtonal MIDI keyboard part. It sends over a virtual CoreMIDI source to GarageBand, Logic, AUM and other hosts, over USB, network MIDI or MIDI hardware. In poly mode each held note takes its own channel, so a quarter-tone chord arrives in tune; mono mode suits a single-channel instrument. Quarter tones travel as a pitch bend on the in-between notes. WHAT IS 24-TET? 24-TET, also written 24 tone equal temperament and closely related to 24 EDO, cuts the octave into 24 equal steps instead of 12. Each step is a quarter tone. It is the tuning behind much modern microtonal and xenharmonic writing, and the usual way Western notation approximates Middle Eastern maqam. It is an equal temperament, not a Just Intonation system. FAQ How do quarter tones work? They divide the semitone in half. 12-TET gives 12 equal steps per octave; 24-TET gives 24, so a new note lands exactly between every pair you already know. Which instruments can play quarter tones? Voices, fretless strings and many winds can bend to them; fixed-pitch keyboards usually cannot, which is what this app changes. Why don't we use quarter tones? Mostly because the instruments cannot play them. An ordinary piano has 12 keys per octave and no room for more. That is the limit this app removes. How do I make microtonal music with it? Play it as it is, or route the MIDI into your DAW and record the quarter tones onto a track like any other part. Can MIDI be microtonal? Yes. Each quarter tone travels as a pitch bend on the in-between notes, one voice per channel, so a chord stays in tune. Does it import Scala or .scl files? No. It plays 12-TET and 24-TET. Is it a tuner? No. It is a keyboard you play. No ads, no account, no analytics, no in-app purchases, no data collected. Want a standalone instrument to just play? Try our companion app Fingerophone. ## Key features - Microtonal keyboard for quarter tones - MIDI output to DAWs - Morphing keyboard layouts - Polyphonic and mono MIDI modes - Visual representation of 24-TET - On-device sound playback ## Recent user reviews (3 of 3) All indexed reviews: https://appshunter.io/ios/app/24-tet-keys-microtonal-midi/id6789963675/reviews.md ### 5/5 — Unique Instrument! *2026-08-29* Full disclosure: I am not a fan of quarter-tones — microtonality, yes, but straight quarter-tones just sound out-of-tune to this Westerner. That said, this is a unique instrument! I would love to see an option of switching to Just tuning (which is its own form of microtonality, but designed to be more harmonically pleasing to Western musical traditions), but one cannot downgrade the developer for straying from the intended purpose of an app that generates quarter-tones only! For instrument sounds, you have the option of piano (kind of a honky-tonk sound), synth (sine-wave), and (Hammond-like) organ. You also have several options on how the “keyboard” is laid out. Props to the developer for this option! My only suggestions are: 1) to have a zoomable keyboard (or to allow for two- or three-tiered rows, so one doesn’t have to scroll to get notes out-of-range of the current keyboard position; and 2) Allow for a full piano range (like the 88 keys in a 12-tone setting) — that the top tone as-is goes only to a B is a bummer — at least finish the C scale out to a top C! :-) Conclusion: Definitely get this app! It is innovative, and it works! (I have not tried it in MIDI mode.) ### 4/5 — Very cool. *2026-08-28* I enjoyed playing around with this. The only thing I’d change is adding the ability to loop a sequence of keys to build up a track and add a guitar/bass sound option. ### 4/5 — How do you import the keys to garageband? *2026-08-02* so far I love this app and I have some ideas: can you allow sampling on this keyboard, maybe allow different experiment tunings such as 31 tet and the ability to zoom in and out of the keyboard to make it bigger or smaller? Next thing, how do you import this to garageband? ## Frequently asked questions about 24 ### How do quarter tones work in 24-TET Keys? Quarter tones divide the semitone in half. While standard 12-TET divides the octave into 12 equal steps, 24-TET divides it into 24, placing a new note exactly between every pair of existing notes. ### Can I use 24-TET Keys with my music software? Yes, 24-TET Keys functions as a compact microtonal MIDI keyboard. It sends MIDI data over CoreMIDI to hosts like GarageBand, Logic, and AUM via USB, network MIDI, or hardware MIDI. ### What is 24-TET? 24-TET stands for 24-tone equal temperament, an alternative tuning system that divides the octave into 24 equal steps, with each step being a quarter tone. It's used in modern microtonal and xenharmonic music. ### Does 24-TET Keys have ads? No, 24-TET Keys does not contain advertisements. ### What devices is 24-TET Keys available on? 24-TET Keys is available for iPhone and iPad. ### How does the morphing keyboard layout work? The app features experimental keyboard layouts that dynamically transform into one another. You can start with a piano-derived layout and morph into others like a domino, honeycomb, or isomorphic layout. ### What is the rating of 24-TET Keys? 24-TET Keys has a high rating of 4.6 stars based on 5 user ratings. ### Is 24-TET Keys suitable for beginners? While the concept of microtonality can be complex, the app's visual morphing layouts and on-device sound playback make it accessible for users to explore quarter tones and experiment with new musical ideas. ## Version history (last 3 releases) ### 1.2 — 2026-07-16 A new isomorphic layout: one move always means the same interval, anywhere on the board. The screen no longer dims while you play. ### 1.1 — 2026-07-15 Three new keyboard layouts and a volume slider. ### 1.0 — 2026-07-14 No release notes. ## More apps by Maxim Oransky - [Apakabar.fm: Bilingual Reader](https://appshunter.io/ios/app/apakabarfm-bilingual-reader/id6745130958) - [Country Count: Travel Tracker](https://appshunter.io/ios/app/country-count-travel-tracker/id6749248063) - [QR Serve: Share Cards & Codes](https://appshunter.io/ios/app/qr-serve-share-cards-and-codes/id6749462083) - [Rachunator: Fiskalni Račun](https://appshunter.io/ios/app/rachunator-fiskalni-racun/id6749515684) - [2000 английских слов](https://appshunter.io/ios/app/2000/id6751864250) - [2000 грузинских слов](https://appshunter.io/ios/app/2000/id6751864471) All apps by Maxim Oransky: https://appshunter.io/developer/1639941241 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-08.*