MIDIWriter is a simple app that transmits MIDI note messages by hitting keys on a keyboard. Playing an input phrase as a sequence is also possible. The tempo and the loop can be set.

You can use either the on-screen software keyboard or a Bluetooth/Lighting-connected hardware keyboard for iOS.

Turn 'BackgroudnAudio' on to hear sound using a CoreMIDI sound generator app running in the background. Compatible apps include ThumbJam, Animoog, Korg Gadget, SampleTank and so on.

You can also play an app running on the other iOS devices and/or Macs using a MIDI Network Session.

Using a background app (Virtual MIDI):

1. Open a sound generator app and enable CoreMIDI and the background mode.

For example, with ThumbJam, turn "Use CoreMidi" and "Active in Background" on in MIDI Control preference. Some apps enable them automatically or by default.

2. Open MIDIWriter and type any key. You'll hear a sound from iPhone. You can also use a external keyboard connected with Bluetooth or the Dock connector.

Using a Mac application (MIDI Network Session):

1. Connect Mac and iPhone to Wi-Fi.

2. Open MIDIWriter on iPhone.

3. Open "Audio MIDI Setup" on Mac and open "Network" in the MIDI Studio window.

4. Click "+" button at the "Sessions" area to create a new session, and click the checkbox to enable the session.

5. If your iPhone is not available in the "Directory" list, click "+" button to create a new device. In this case, set your iPhone's IP address to the "Host" field and give a certain name and a certain port number (ex. 5004).

6. Click your iPhone in the "Directory" list to select it, and click "Connect" button to add it to the session.

7. Open a CoreMIDI compatible sound generator application (ex. Ableton Live) on Mac, and choose the network session for the MIDI input port.

8. Type any key on MIDIWriter. You'll hear a sound from Mac. You can also use a external keyboard connected to iPhone via Bluetooth or the Lightning connector.

What's New

Version 1.2.0

64bit compatible

Ratings and Reviews

Not quite fun enough to be a toy


A buck isn't much money, but I don't think I got a dollar's worth of pleasure out of this. There's no way of knowing what note will get played when a key is depressed, and no way to specify or control that. Also, the app starts in a mode in which each key typed produces a note (again, you get no control of the note's duration), but if keyboard focus is ever once given to the text field, you're stuck in a "batch" mode from then on, and can't get back to the key-by-key mode.

It's sort of a pity, because — viewed as a proof of concept exercise — it's actually a potentially interesting idea, and might allow the use of an external bluetooth keyboard (for instance) to quickly audition the sounds of a MIDI synthesizer, without either setting up any external MIDI hardware, nor using the on-screen keyboard within the synthesizer app. As it is, it seems that the developer just got something more-or-less working, and then "threw it out there" to see if anybody would pay for it. Well, I did pay for it, but would encourage you not to.

To summarize, it's not all that much fun to play with after the first 20 seconds or so, when it's been established that typing a key can, in fact, cause a sound to be played. And although the fun value is limited, the app's use for more than that is non-existant.



Very little documentation, no way to adjust settings, holding a key sends a rapid signal instead of a sustain. I tried this with animoog, and the number keys gave me middle notes while EVERY OTHER KEY was at the high end of the scale — so there really isn't much range for this.

Fancy idea, but not really executed well. Hope they develop it more.


正行 Akamatsu
1.2 MB
Requires iOS 10.0 or later. Compatible with iPhone, iPad, and iPod touch.
English, Japanese
Age Rating
Rated 4+
© Masayuki Akamatsu


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