U-Plex + MidiBridge = microtonal iPad, iOS

June 14, 2012

In 2009, I received an order for a TBX1 unit from Michigan-based sound artist Mitchell Walcott. Two years later, another order from Mitch appeared, this time for a custom finish two-octave U-Plex keyboard all white (shown above) similar to the Moby Plexus TPX unit I had made for color-blind composer Jesus Lopez in 2010. Little did I know what Mitch had in mind for his keyboard.

Shortly after I shipped the white U-Plex to Mitch, I received an email from him, asking about the possibility for connecting the keyboard to an iPad through Apple's USB camera connection kit. This was something I had wondered about myself, but had no way to test. Since I don't develop for iOS (the operating system used on Apple's iPads and iPods), and U-Plex outputs only untuned raw MIDI, I thought it was probably not possible to get the keyboard to produce microtonal output on iOS, but Mitch was more optimistic.

A little background for anyone unfamiliar with all this iPads were originally cut off from the world of MIDI hardware, apart from a few companies who were able to design special interfaces for the iDevice docking system. Then Apple released the USB connection kit, which is compatible with the second generation iPad and later. Although marketed to photo enthusiasts, the connector also allows USB MIDI devices to connect to iPad2 without a pricey third-party gizmo. An update to iOS followed shortly after the release of the connector which added CoreMIDI support to iOS, and since then, development of MIDI apps on iOS has become much easier; instead of developers resorting to clever workarounds, they can now just call directly to Apple's programming framework.

In January of 2012, another email appeared in my in box, this time a CC on a note from Mitch to audeonic developer Nic Grant, who is based in Ireland. Mitch offered to hire Nic to add support for Tonal Plexus keyboards to his app MidiBridge, a brilliant little app which runs in the background of iOS and routes MIDI between any and all iOS MIDI ports; physical, network and virtual.

That very same day, Nic responded in the affirmative, and to my amazement, the project was underway.

Prior to instigating all this, Mitch had been busy contacting various iOS synth designers to find out about possible candidates for an iOS U-Plex controlled microtonal synth. Homework! I joined in the search, and corresponded with the folks at crimson technology, makers of iOS wavesynth, to find out about the possibility of adding CoreMIDI support. Sure enough, in April crimson added the necessary support.

Beyond a little bit of fiddling with iPod touch units to test MIDI over WiFi, I didn't do much other than supply some documentation and correspondence with Nic and Mitch, answering questions and trying to keep up with the quick pace of Nic's progress.

Long story short, here we are half a year later, and Mitch's vision is a reality - U-Plex works with iOS synthesizers through MidiBridge! The basic requirements of an iOS synth app are as follows:

If the above requirements are met, it's just a matter of setting up MidiBridge to listen for input from U-Plex, process the input with the brilliant H-Pi microtuner programmed by Nic, and the U-Plex can control the synth and produce microtonal polyphony on iOS. Here are a few synth apps tested and approved to work with U-Plex and MidiBridge:

Now I shall clear the stage for the real stars of this show, Mitch and Nic. Mitch Walcott writes:

Exploration in Sound "The idea of discovering new sounds is intriguing to me. This is what prompted me to purchase a U-PLEX keyboard controller from H-Pi Instruments. I wanted to further investigate microtonal music and I asked Aaron Hunt to build one for me. Because of my preference for the iOS platform, I wanted the ability to use my U-PLEX keyboard with different synthesizer apps. After researching what possibilities were available, I found that iOS developer Nic Grant (Audeonic) grasped the concept and was interested in the project. Numerous e-mails and bench testing then ensued between Nic, Aaron, and myself. A modified version of Nic's MidiBridge app ultimately made this all possible. Some synthesizer apps already work accurately with the combination of MidiBridge and U-PLEX. My hope is that other iOS developers will listen to our suggestions on MIDI implementation in order for their apps to also obtain correct microtonal capabilities. Using my iPad, my U-PLEX controller, MidiBridge, and various synthesizer apps will become my preferred method of sound exploration."

Nic Grant of audeonic says:

"Mitch approached me with a view to adding support for the H-Pi U-Plex to MidiBridge in order to bring H-Pi to iOS. With Aaron's excellent documentation and superb support, I was able to implement H-Pi's microtuning algorithms into MidiBridge without too much trouble at all. The difficulty we faced after making the changes was finding the right iOS synths that would be able to handle to retuned MIDI data. Luckily some excellent synths could handle per channel pitchbend like Arctic Keys, Thumbjam and Wavesynth so we were in business!"

In the coming days I'll be updating the website to include links to MidiBridge, and possibly other iOS apps that are proven by Mitch to work with MidiBridge.

I should mention that the H-Pi microtuner on MidiBridge can also be used on iPhone and iPod touch, to retune incoming MIDI over WiFi. Though I wasn't able to test this completely myself, Nic Grant assures me that with a good network connection you should be able to play your U-Plex and send the output to your iPod running MidiBridge + your favorite multi-channel MIDI app and use your iPod as a microtonal synth engine for your U-Plex.

Additionally, TPX owners need not flinch at the USB-only connectivity, since special iPad MIDI interfaces like the Line6 Midi Mobilizer (I & II) and IK's iRig MIDI can connect TPX keyboards through conventional MIDI cables to iPods, iPhones, and iPads.

What can I say about all this, but that I'm very grateful for Mitch Walcott's enthusiasm and generosity, for Nic Grant's iOS finesse and patience, and and for the pleasure of seeing new ground broken to open up new possibilities in music making.

By the way, here is a U-Plex similar to the one I made for Mitch, which was recently requested by a customer in Germany. You may notice that the design of the body is slightly improved.

More to come; I have many photos from keyboards built over the last year, which I plan to show in the blog soon.

Thanks again to Mitch and Nic for making good things happen!

* photo of Mitch Walcott by Erin Meekhof Sturgill

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