Thor: Reason’s Powerhouse Synth Goes Mobile

Asking fans of Propellerhead’s Reason software what keeps them coming back, you’ll hear a lot of answers about how modular it is, how creatively inspiring…but you’ll also hear about Thor.

The flagship synth has been the heart and soul of Reason since its introduction in version 4 of the desktop software, and now we can harness that power wherever we go with Thor for iPad. But does the mobile music world have room for another synth? We put Thor through its paces to find out!

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Open Concept Synthesis

Part of Thor’s appeal has always been that it embodies much of what makes Reason itself so much fun to use: it doesn’t impose many restrictions on how you can use the tools, preferring to offer you a panoply of routing options and trust in your ability and curiosity to do the rest.

Thor is structured as a series of configurable slots into which you can load 3 different oscillators of different sorts, three filters, and then choose how the signal is routed through the synth. This opens up a world of possibilities and makes it hard to categorize Thor beyond calling it a very capable subtractive synth.

Touching a God

Taking such a complex instrument and translating the experience to a touchscreen is no easy feat. Asked about the process, product manager Kalle Paulsson said, “we wanted to eliminate some of the stuff that’s usually done with the interface when there’s lots of controls that need to share a common space,” explaining that through the design process they “looked at a lot of different ways to achieve that.”

Meet Thor, thunderous mobile synth extraordinaire.

Meet Thor, thunderous mobile synth extraordinaire.

In the end, we’re left with a clean interface reminiscent of the wildly successful Figure, while retaining the familiar modules that Thor users will recognize, albeit organized into three sections.

The app opens in the Keyboard section, which displays Thor’s assignable modulation knobs and basic keyboard controls arranged above a wonderful flat keyboard with some incredibly clever functionality that we’ll have a look at later. The red header remains consistent across all sections of the app and gives instant access to the patch browser and app settings.

No shortage of controls to fiddle with in Thor's Knobs section.

No shortage of controls to fiddle with in Thor’s Knobs section.

The Knobs section, accessible from the tab in the header’s right side, shows us the meat & potatoes of what’s going on, allowing us to modify the oscillator and filter modules as well as adjusting the LFO, envelope, and effects settings. Each section intelligently expands and collapses to effectively use the screen real estate to give focus to what you’re adjusting.

Notice that the knobs are much easier to use than you might imagine: though Thor sports a fairly skeumorphic overall aesthetic, the knobs are very responsive and reveal floating bars to help you dial in a precise setting as soon as you’ve tapped. This is a slick way to keep the same visual feel without compromising usability via touch.

Scary but powerful: Thor's routing section.

Scary but powerful: Thor’s routing section.

Lastly, the Routing section reveals what desktop Reason users will recognize as the modulation matrix, where modulation sources and destinations can be paired for crafting complex patches that truly take advantage of the engine. Also present is Thor’s sequencer, which runs synced to the master tempo or runs free with a nice wide range.

Let’s take a closer look…

Magical Keys

We’ve seen a number of innovative approaches to translating the physical keyboard to a touch interface. The simplest method is to simply make a digital replica, but that hardly takes advantage of the capabilities that make the iPad so exciting for music producers.

Thankfully, we have examples like Animoog, Waldorf Nave, and now Thor to show us how even core tenets of synth interaction are ripe for improvement.

Since the iPad screen is incapable of sensing touch pressure, the slender keys take into account where on the key itself you touch and translate that into MIDI velocity information—higher up on the keys produces softer velocities, while playing on the lower tips is equivalent to playing hard on a real keyboard. This is perhaps unintuitive when you may be tempted to think that higher touch position = higher MIDI velocity, but it’s easy to get used to. Tapping and dragging also invokes aftertouch (for patches that use it as a modulation source), which is perfect for expressive playing.

The Keyboard section was clearly designed for performers, with three helpful views. The first looks just like a normal keyboard, with all notes arranged chromatically and available to play. If you want to restrict playable keys to a certain key signature or scale, you can use the Assist button to do so.

Use Assist to define a key signature, and Collapse to remove any notes that don't conform!

Use Assist to define a key signature, and Collapse to remove any notes that don’t conform!

After picking a desired key and number of notes per octave using the Key and Colour menus, respectively, you can activate the Collapse mode to remove any “wrong” notes and leave only notes conforming to your Assist settings visible. You can then hide the Assist panel and slide out the Modulation one to give you access to a virtual mod and pitch wheel for true synth-like playing.

The Keyboard section has one last trick up its sleeve: strum mode. When active, you’ll see an extra two touch areas appear on the right side of the keyboard. Now, instead of notes triggering when you touch the keys, you’ll have to hold down a chord and then “strum” the virtual strings that appear in the Strum lane to simulate guitar playing. The Hit area allows you to trigger all the notes in the chord at once for a more quantized feel. The Hit lane is also sensitive to velocity control in the same way the keys are.

Show or hide the Modulation section, or play with Strum mode to simulate guitar playing.

Show or hide the Modulation section, or play with Strum mode to simulate guitar playing.

It’s worth mentioning that once you’ve set the keyboard up as you like it, Thor will remember the settings for the next time you launch. Very gentlemanly.


While you could conceivably spend your entire Thor experience in the Keyboard section, doing nothing but picking patches and playing them while adjusting whatever parameters have been mapped to the two control knobs, this is barely scratching the surface of what Thor offers.

To truly appreciate its power, we have to dive into the Knobs section.

Here, we find ourselves confronted by the three oscillator slots by default, with the first two filter slots beside them. If we use the patch menu to load the “Simple Analog (Reset)” patch from the Templates tab, we get pretty close to a clean slate.

A clean slate clearly shows us the available module slots.

A clean slate clearly shows us the available module slots.

While reverse engineering complex patches is a great way to learn, starting from scratch allows us to really understand how Thor makes sound and how that sound travels from the oscillators to the output. In each of the Oscillator slots, we can load one of the six available modules, each providing a different character of sound generation.

Next, we can follow the arrows to the Mixer, where we adjust the ratio between the levels of each oscillator, allowing us to fine-tune the balance of raw sound. The refined oscillator output then travels to the Filter section, where we can choose to bypass certain oscillators and run only one through the first filter and the other two through the second filter, for example, or run everything through both filters in parallel.

After optionally passing through the Shaper (essentially a distortion module), we pass to the next expandable section of this view where LFO 1 and the envelopes live. There are three dedicated envelopes, one for Filter, Mod, and Amplitude, and the sound’s primary gain, pan, and velocity sensitivity can be adjusted here in the Amp module.

Lastly, the sound is delivered to the last expandable section where it can be run through a Delay and/or Chorus module, as well as the third and final Global Filter. Also in this area, you’ll find the second LFO and the freely-assignable Global Envelope.

The far side of the Knobs section is where we put the finishing touches on the sound.

The far side of the Knobs section is where we put the finishing touches on the sound.

Enter the Matrix

If you’re really feeling ambitious, then you’ll find yourself in Thor’s third and final section before long: Routing.

There are two main components to this section, the first of which is the nominal routing area where you take care of everything to do with modulation. There are seven standard routing slots, four dual-destination slots, and two dual-scale slots available here.

Many modulation slots offer endless routing possibilities.

Many modulation slots offer endless routing possibilities.

If you have no idea what I’m talking about, don’t worry—this is where synthesis gets complicated. Essentially, the purpose of this entire section is to allow you to make Thor wiggle knobs automatically without you having to touch anything. You could use LFO 1 to modulate pitch in time with your tempo to make a nice wobble effect, or assign the filter cutoff frequency to your modwheel for easy sweeps. The possibilities are endless and I highly encourage you to experiment, as a full tutorial is beyond the scope of this review.

The second component, taking up the bottom half of the screen, is the Sequencer. Thor sports a step sequencer similar to the ones found on analogue modular gear. It’s ideal for programming patterns and offers a surprising array of run modes, directions, and step parameters.

The Sequencer is a powerful pattern engine, not to be overlooked as you explore.

The Sequencer is a powerful pattern engine, not to be overlooked as you explore.

Whether you’re using it as a simple arpeggiator or wiring it into a complicated modulation setup, the sequencer is a capable and welcome addition to Thor’s vast capabilities.

Sound Design

According to Kalle, the priority for Propellerhead’s mobile efforts has always been “helping people produce more and better music than ever before, wherever they are, with however much time they have on hand at that moment.” This underlying expectation is evident in every detail of Thor’s design, and the fact that it does not come at the expense of horsepower and familiarity for power users is remarkable.

Thor on the iPad uses the same engine as it does on its desktop equivalent—behold the face of progress in the tablet world—so you can expect the same pristine audio quality, with full-bodied oscillators and filters with enough character and versatility to cover most synth scenarios.

Being a subtractive synth at heart, you won’t find any complicated physical-modeling style sounds like you can get with an additive synth, and you can’t really mimic the unique sound of granular synthesis, but Thor isn’t trying to cover that ground.

Taken as a collection of parts, Thor isn’t necessarily the best out there—Waldorf’s Nave easily bests it for wavetable synthesis, for instance—but Thor is more than the sum of its parts, and it is easily one of the App Store’s most versatile and inspirational synths.

It aims to bring together a familiar set of modules in a way that allows a wide audience of synth enthusiasts to produce music and be inspired on the go. Less progressive than Animoog, but more accessible.

Communicating With the Mothership

Of course, you’d expect that with all this engine synergy between Thor on the iPad and Thor in Reason, the two would communicate smoothly—and you’d be right!

Using iTunes file transfer, you can easily move patches back and forth between the desktop and iPad versions of Thor, which can be handy for starting a new patch on the go and refining it back at the studio, or crafting a patch at home and sending it to the iPad for live performance.

Needless to say, AudioBus compatibility is also present, allowing you to route Thor’s audio out to other audio apps, and full MIDI capabilities mean you can play it using a real keyboard or sequence it from another app on your iPad. Thor plays very well with others.

Final Words

Most limitations in Thor are part of its charm. Those coming to it fresh, without any Reason familiarity, may find the interface a bit cluttered and needlessly 3D. They wouldn’t be wrong, but the design wasn’t just motivated by keeping things friendly to Propellerhead fans: consolidating sections as much as possible means that you’re never more than a couple of taps away from adjusting any parameter in the synth.

Nevertheless, the developers will hopefully continue to refine the responsiveness of some of the knobs, and as far as new functionality, being able to wirelessly sync patches between your desktop and iPad would also be amazing. There has to be room to grow somewhere.

As it stands, Thor casts a wide net and snags a lot of eager synth enthusiasts in the process. As Kalle puts it, “we like the many synths available on the iPad and wanted to contribute with own flavour.” Thor is a jack-of-all-trades with a solid mastery of most of them, which is high praise for a synth in any environment. The fact that it lives on your iPad and costs as much as your average movie ticket makes it a very flavourful contribution indeed.


Thor is a versatile and powerful instrument that offers a wide palette of synth capabilities without being unwieldy.