XK-1 review – One Red Dog make things easy with streamlined synth

Download from iTunes App StoreXK-1 logoDeveloper One Red Dog Media have been around on the App Store for some time. They have released a number of iOS music apps including Arctic Keys and Molten Drum Machine. However, my favourite app is Arctic ProSynth which I reviewed when it was first launched back in late September 2013. Arctic ProSynth is a very clever bit of design; it has a clean user interface that strikes a good balance between enough features to keep the programmers happy but without being so busy that wannabe synth programmers are not put off.

Oh, and if you just want to pick a preset and play, then is sounds fabulous also… aggressive and modern sounding, the subtractive synth engine is actually surprisingly versatile. And with both Audiobus and IAA support, and a very good MIDI spec, the app is easy to build into a wider iOS music production workflow.

Of course, not everyone wants to be a synth programmer and, even if you do like to get your hands dirty at times, there is always an occasion when you just want to fire up a synth instrument and play. Well, One Red Dog now have that base covered as well; their latest release – the XK-1 synth – is designed to do just that. So, with a starting price of ‘free’, if you are just looking for some preset fun, is the XK-1 worth a punt?

XK-1's main screen; about as simple as a synth's control set can get?

XK-1’s main screen; about as simple as a synth’s control set can get?


For what is actually such a simple instrument, the XK-1 is quite an interesting concept. It represents a collaboration between One Red Dog and CME. The latter are well known for their MIDI devices including a range of highly regarded MIDI controller keyboards (I use one of their 88-note keyboards – a UF8 – as my main master keyboard in my desktop-based studio). They are also the makers of the rather stylish 25-key Xkey keyboard designed specifically for use with an iOS device and to be ultra portable. I reviewed the Xkey a little while back and was so impressed that I bought the review unit (and, incidentally, there is now a 37 key version on the way).

When you see the main screen of XK-1, it is divided into three parts; a upper control strip for patch selection and accessing the Settings menu, an X-Y pad with two nodes for finger control of various synth parameters and, at the base, a virtual keyboard in the (graphical) style of the CME Xkey. This virtual keyboard operates as any other and, in addition, you can hook up any standard external MIDI keyboard and play the XK-1 with that.

Once you have obtained the IAP, you get a full preset browser that opens when you tap the preset box.

Once you have obtained the IAP, you get a full preset browser that opens when you tap the preset box.

However, if you happen to have an Xkey, it will save you the price of the UK£1.49 IAP required to unlock the additional sound set for the synth. By default, the free base app gets you the XK-1 supplied with 16 presets. If you cough up for the IAP, this adds a further 168 presets covering a wide range of sound types and organised into groups based upon instrument type (bass, lead, pad, etc.). However, if you plug in your Xkey hardware, this automatically unlocks the IAP for you. This worked fine for me (and, by the way, the presets stayed unlocked even when I plugged in a different MIDI keyboard controller).

Just play….

In use, the XK-1 really is as simple as it can get. You pick a preset (and, without the IAP, this is just done by stepping through the available presets using the two small arrow buttons located beside the preset name) and start playing. The virtual keyboard performs nicely and includes a ribbon-style pitch-bend control on the left edge. For each preset, the two nodes in the upper X-Y pad are linked to key synth parameters and generally seem to control aspects of the filter and EQ.

The XK-1 has both Audiobus and IAA support.

The XK-1 has both Audiobus and IAA support.

So, visually, the XK-1 is a triumph of simplicity and that is reflected in how you can play it; select a preset, hit some notes and tweak the Y-Y controls to add some movement to the sound….   and that’s about it. You can’t dig in to any of the other elements of the synth, there are no MIDI parameters to tweak and you can’t create and then save your own presets. This is designed simply to allow you to plug in and play…..

What else?

That said, the XK-1 does have Audiobus support and can also be used via IAA. If you want to add some further effects processing (for example, via Audiobus), then that’s perfectly possible. Equally, the XK-1 can receive MIDI data from external keyboards of from another iOS app (I had no problems selecting it as an MIDI destination from a Cubasis MIDI track).

Having tried the app within Audiobus, it worked very much as expected. Used via IAA within Cubasis, it did take some setting up (mainly because the XK-1 seems to be ‘invisible’ in the list of IAA apps within Cubasis when you try to select it; just tap on the blank entry. Hopefully this bug will be addressed in an update). However, once I worked my way around that, it worked fine and I was able to get both audio and MIDI data to work as required and the XK-1 has a nice IAA transport panel when used in IAA mode.

The XK-1 was able to receive MIDI from Cubasis quite happily so it is not just useful for a 'plug & play' performance role.

The XK-1 was able to receive MIDI from Cubasis quite happily so it is not just useful for a ‘plug & play’ performance role.

There is, however, one further ‘what else?’ comment to make. The XK-1’s synth engine only really offers you limited amount of sound editing options (those two X-Y nodes) although it does also support polyphonic aftertouch (as supplied by the CME Xkey). However, that engine is based upon that same engine as found in the excellent Arctic ProSynth. The ability to tweak sound and create your own presets may be limited but the actual sound quality of the presets is not.

Indeed, the XK-1 sounds very good indeed. Fired up through a decent monitoring system – and with my CME Xkey connected – it is kind of scary that such a minimalist setup with such a streamlined looking virtual synth could sound so good and I managed to while away a very happy couple of hours exploring the various presets. Add in your choice of iOS audio effects apps via Audiobus and there is plenty of scope for some very impressive sound creation.

In keeping with the KISS principle, the XK-1's Settings menu is pretty simple, although you can set the tempo which, in turn, then sync any of the sounds that include apreggio patterns.

In keeping with the KISS principle, the XK-1’s Settings menu is pretty simple, although you can set the tempo which, in turn, then sync any of the sounds that include apreggio patterns.

In summary

The XK-1 sounds great and I like the idea of the minimalist design. It really is aimed at those occasions when you just want to plug in and play without being distracted by the possibility of tweaking a modulation matrix or adjusting an LFO sync mode. Instant sound in an easy to use package…..

As a free download, the base app does offer you a way to try before at low cost but I suspect most folk will soon tire of just the 16 presets. The IAP is, therefore, pretty much essential if you really want to get the most out of the app. The quality of the sounds is very good so, even having spent that UK£1.49, I don’t think most users would have much to complain about. It will be interesting to see if One Red Dog offer further sounds via future updates and/or additional IAPs.

If you are an experienced synth-head and have a shed full of iOS synths already, then the XK-1 might not offer you anything over and above what you already have (particularly if you already own the excellent Arctic ProSynth). However, if you are just after a streamlined,  easy to use iOS synth but which packs a sound well above its weight, then One Red Dog’s XK-1 is well worth checking out.

XK-1 synth

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    1. It wasn’t clear to me at first, but it is a Free download. Since I’m always running out of time (thus no time for synth patch tweaking) this app fits right in to my workflow, and I immediately splurged and spent $1.99 (plus tax) on the IAP for all of the voices.

      On a quick run through the voices I checked sounded really good….and seems like there is quite a nice variety of sounds.

      Thanks for posting about this John, for me I can already tell it’s a couple of bucks well spent!!!

      -Toz Bourne

      • Hi Toz…. yes, the base app is free. According to Peter Johnson of One Red Dog, there was a mistake when it first appeared on the the App Store and a listing price of UK£0.69. That’s now been corrected…. best wishes, John.

    2. Jayson Vein says:

      Great free app, haven’t got the IAP yet, but plan to. Lots of presets for a great price. When it comes to synths, I’m all about the presets. They make me feel warm and fuzzy, and save me loads of time.

    3. Chris Catalano says:

      Agreed about presets, more or less, even though I end up tweaking them. I do so much DIY as far as playing, singing, arranging, writing, mixing…but you know, when I buy a synth app, I want to know what it CAN do, right out of the box. Painting with oil for 30 years, I have zero need or time to grind my own pigments, when there are experts who can do it way better that I ever can. I don’t need to build my own guitars to make music, or play them well, and similarly with synths, it is often best to leave the original programming to the sound designers who understand synthesis at the deepest level: musical and timbral, and then maybe take off from there. Man, there are folks out there who insist it is not possible to create original music using patches created by developers. Uh, no. It is very possible, and you do not need a programmer’s licence to use most of the best synths out there. An understanding of musical context, composition is WAY more important for most of us when creating music, NOT building patches from scratch. Not to say that is not a noble and cool aspiration for many, but being able to do that does not guarantee quality music in any way shape or form. A friendly reminder (sort of) for a few synth purists out there, ever waiting to point out that “if you didn’t build the instrument from scratch you are not doing it right”…You know where you can stick that patch next time you remind me of that, lol…

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