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  • Korg plugKEY Mobile MIDI/Audio Interface For iOS

    By Phil O'Keefe |

    Korg plugKEY

    Is this the iOS MIDI / audio interface for you?



    by Phil O'Keefe






    Own a fairly recent iPad or iPhone? Apple's various iOS devices have been overwhelmingly well-received by musicians, and with the wide range of useful music-oriented apps that are available, why wouldn't they be? But they're far from perfect; many of the features you'll find on Apple's mobile devices are less than ideal from a musician's perspective, and some important features are missing entirely. Some of those areas have to do with the very limited I/O that iOS devices have built-in; you get a mini stereo headphone output, a Lightning input port, and basically that's it. But Korg has a solution, and it's something that many iOS device-owning musicians will be interested in - the Korg plugKEY.  


    plugkeys-342166c9.jpg.ca213e8e94a78efdda9b1de4bd629aa7.jpgWhat You Need To Know

    • The Korg plugKEY is a small (2.91" W x 2.36" D x 0.91" H) mobile MIDI / audio interface designed specifically for iOS devices running iOS 8 or later, and that include a Lightning port.
    • It's "Made for iPhone / iPad" certified by Apple, so compatibility is assured - at least until the next time Apple changes their ports. 
    • The review sample that I was sent for testing has a white housing, while other examples I've seen online have a black one. Korg uses a -BK or -WH product name suffix to indicate the housing color, but I've yet to see a dealer who offered you a choice.


    • A blue LED on the rear corner of the unit illuminates when it's connected to a iOS device.



    • While small and light in overall weight (a mere 2.43 ounces), the plastic housing of the plugKEY seems sturdy enough - no doubt aided by its compact dimensions, thick plastic, and rectangular "brick" shape.



    • The MIDI interface section of the plugKEY consists of a single 5-pin DIN MIDI input jack. This is perfect for getting MIDI information into your iOS device from your controller, sequencer or DAW's audio / MIDI interface - as long as your controller, interface or sequencer has a 5-pin MIDI output.


    • It doesn't just work with MIDI note on/off commands. MIDI CC data for functions like your controller's pitch and mod wheels, sustain footswitch, foot pedal, and the like are transmitted to the iOS device too. This allows much greater expressive control than what's available from your iOS app's built-in virtual keyboard.


    • The audio interface supports both 16- and 24-bit operation at 44.1 kHz and 48 kHz. The two audio sections of the plugKEY are on opposite ends of the device. Next to the MIDI input jack you'll find a 1/8" stereo headphone output jack and associated volume control.


    • On the opposite side of the unit (next to the permanently attached one foot long Lightning  cable) is a pair of unbalanced 1/4" output jacks, which are labeled L (mono) / R on the underside of the unit. In fact, everything is labeled on the underside. While not really terribly necessary since there are so few ports and controls, it is convenient that they're labeled - although the labels would be somewhat more useful if they were on the top surface instead of the bottom.


    • While the plugKEY can be bus-powered (drawing its power from the connected iOS device), it does have another trick up its sleeve, courtesy of the micro-B USB port on the right side of the unit: the ability to charge your iOS device while you're using it. You'll need to supply a suitable micro-B USB cable and 5V USB AC power brick (or a USB power bank like the one I discuss in my article on Using Bus-Powered Hardware MIDI Controllers with iPad Apps) and connect them to the plugKEY, but once you do, the connected iOS device will start charging. 



    • There is no USB MIDI support. This means you'll need a MIDI controller with a 5-pin MIDI output jack, and while most MIDI keyboard synths still have these kinds of ports and  can function fine as a controller, MIDI controllers with 5-pin DIN jacks are becoming more and more scarce. With most of the currently available low-cost controllers sporting only USB MIDI output jacks, you may have to scramble a bit to find a compatible controller or USB-to-5-pin adapter.


    • There's no audio input on the plugKEY, which means the plugKEY isn't a good interface for audio recording.


    • There is no MIDI output jack either. Since iOS devices have various ways that they can store and save data this isn't a terribly bothersome omission, although a MIDI output would still come in handy for sync and other MIDI applications.





    The plugKEY is an interesting little box that provides a lot of added capabilities to your Lightning port-equipped iOS device. It gives your iOS device a MIDI input, as well as a more robust set of 1/4" line output jacks. And while the internal speaker is disabled when the plugKEY connects to your iOS device, that's usually what you want when you're using line outputs anyway. You can still monitor directly using the onboard 1/8" stereo headphone output jack on the plugKEY, although the level of that output is tied directly to the built-in volume knob. This also controls the output level of the line output jacks, so their levels can not be adjusted separately.



    The Korg plugKEY weighs practically nothing, is easy to take with you, and seems more than rugged enough to survive numerous journeys. Best of all, it's quiet - there's no appreciable hiss or noise from the 1/4" outputs to annoy you or add unwanted grunge to your recordings or performances. Even the headphone output is fairly quiet, and both the line and headphone outs have plenty of level.



    I think a wide range of users will appreciate what the Korg plugKEY has to offer. It's useful for iPhone 7 owners who want to continue to use the headphones they already own that have a 1/8" (3.5mm) stereo plug, and it's excellent for those who want to use an iOS device running a virtual instrument in a recording studio or live performance situation because the 5-pin MIDI input is compatible with anything that sports a regular 5 pin DIN MIDI output jack.


    Unfortunately it seems that today's inexpensive controllers often don't have such jacks, and since there's no USB MIDI input on the plugKEY (the micro-B USB port works only for powering and charging the connected iOS device), you can't use it with MIDI controllers that only have USB outputs. The lack of audio inputs also means you can't use the plugKEY for audio recording.


    For use with a computer or controller that has an old-school 5 pin MIDI output it works great, but I can't help but hope that Korg has a next-generation model in the works with added 1/4" line inputs, 5 pin MIDI Out and USB MIDI. It would have to be a bit larger to accommodate the extra jacks and ports, but I'm sure many players would consider it a worthwhile tradeoff. Such a unit would quite possibly be the ultimate mobile iOS audio / MIDI interface. As it stands, the plugKEY is simply a very useful one. -HC-


    Have questions about the review or want to talk about the Korg plugKEY? Then come on over to the Keys, Synths and Samplers forum and join the discussion!






    Korg plugKEY MIDI / audio interface for iOS with Lightning Connector ($130 MSRP, $99 "street")


    Korg's product web page    



    You can purchase the Korg plugKEY MIDI / audio interface from:



    Guitar Center    

    B&H Photo Video

    Musician's Friend    














    Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.  

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