Under The Microscope

The Design of Audio Hijack 4

Earlier this year, we shipped a massive upgrade to our flagship audio recorder, Audio Hijack. In addition to over 100 new features, Audio Hijack 4 also includes an overhauled design. Without a doubt, this was the biggest design project I’ve tackled as Rogue Amoeba’s designer, and probably in my entire career. Now that it’s out, I can take you behind the scenes and show you how we went from design goals and sketches to a polished app.

Multiple Design Goals

When considering what to do for the new version, I worked out some clear design goals. Audio Hijack 3 was originally released in 2015, and it provided a great foundation. However, I knew there were places we could improve.

Less Visual Clutter: While I loved design of Audio Hijack 3, fantastically executed by Rogue Amoeba’s previous designer Christa, I felt it could be made cleaner and simpler. Audio Hijack’s critical functionality is found in the custom setups called sessions, which users create to capture and manipulate audio. I wanted to make the rest of the interface deferential to each session’s audio grid.

A More Functional Sessions List: Audio Hijack sessions are reusable and saved automatically. The list of saved sessions serves as the starting point for the app, and I wanted to improve that window by showing more details about sessions, as well as allowing the user to access basic controls without having to open them.

Better Navigation: In the previous version of Audio Hijack, a session’s recordings and timers were kept in a separate window, rather than being closely tied to each session. I felt this was something I could make flow more logically.

A Brighter, More Kinetic App: Audio Hijack 3 had a somewhat muted look, and I wanted to brighten the new version. From day one, we knew we’d be adding a new “Light” theme, but I also sought to add splashes of colour throughout the app. Our apps have also been trending towards having more and more movement, so it made sense to liven things up by adding more animation.

New App Icon: Finally, I was excited to make a new icon for the new version.

Let’s look at some of the ways we accomplished these various goals.

Reducing Clutter and Adding Colour

The design of Audio Hijack 4 came together over a long period of time. The node-based UI introduced in version 3 was a huge success, so we knew we wanted to keep that general concept intact, while improving myriad facets of it. I dabbled with various ideas off and on for quite some time, while our amazing developer Grant worked on the underlying code and new features.

Early Mocks

This is the very first mockup that I could find for version 4:

It shows just two blocks, but the connecting wire is surprisingly similar to what we ended up shipping. I knew right away that I wanted curved wires, though I was unsure if they would be worth the development effort. I also experimented with small icons under the block titles. This was quickly axed, however, because it led to too many cases where we needed to split block titles onto two lines.

In this next mock, I tried having tiles snap directly together. It’s an idea I still like, but it hasn’t yet made it past this concept phase:

These first two mockups also show that the colour scheme was fluctuating wildly. Both contained Audio Hijack’s signature oranges and blues, but the feel wasn’t figured out yet.

Getting There

Over time, my mockups moved closer to the app’s final form, and contained more and more of the eventual interface, as seen in the following mock:

This particular mockup is almost a halfway point between versions 3 and 4. The colours temporarily swung back towards version 3’s darker hues and the connecting wires have reverted back to straight. However, the sidebar on the right looks similar to the final product, with a reduction of the more ornate elements of the old UI.

Left: Version 3; Right: Version 4

The above screenshots zoom in on the shipping sidebars for version 3 and version 4. You can see the boxes around each group of blocks were removed, icons were enlarged, and the text was given more space. None of these were major changes, but together, they served to simplify the interface as a whole.

In this last mock, the app really started to look like what we eventually shipped, complete with the new “Light” theme:

This shot shows several ways we simplified the UI. The bottom bar in particular is a lot less complicated, and no longer extends all the way across the window. We also replaced multiple disparate views with tabs in the sidebar – more on that below. Even those great curved wires feel cleaner visually.

P3 Colours

One noticeable change between these early mocks and the shipping version is the implementation of brighter colours. The blues and oranges in Audio Hijack 4 dip into the territory of ‘P3’ colours, which display a little more vividly on newer monitors. Macs have shipped with P3 colour support for quite a few years, but this is the first time we felt it worth using throughout a whole app’s UI.

An approximation of the difference between standard sRGB color and brighter, more intense P3 colour.

You can only see P3 colour on a P3 monitor, but the above image gives an approximation of the relative difference. It’s subtle, but the non-P3 gradient on the bottom is less bright and dynamic than the P3 gradient on the top. Using the P3 colour system, we were able to make colours more intense than we could before.

To avoid overwhelming your eyes, these brighter colours are used sparingly, generally when we want to draw your attention. In our very basic array of colours, we use a bright orange to denote when something is “live”, and this extra pop of P3 intensity for the orange makes this important status just a little more eye-catching and harder to miss.

Enhanced Navigation via a More Powerful Session Sidebar

One of my biggest frustrations with Audio Hijack 3 was the navigational architecture of the app, which divided much of the content across different windows. For example, after you made a recording with a session, you then needed to open the Home window’s “Recordings” tab to access your audio. There, the recording was shown in a list with other sessions and their recordings. Schedules suffered from similar issues. It all worked, but the recordings and schedules for a session were not closely tied to the session itself, and I often found myself taking a few seconds to try and remember where to find them.

To improve this, we built out a much more powerful sidebar for the session window, one which incorporates these related items. The sidebar is already literally attached to the session, and thanks to the power of tabs, it now holds that session’s recordings, schedules, and even the newly-added scripting features. Sessions are now fully self-contained, and it works wonderfully.

An Improved Session List

Another element of the UI we wanted to improve was the list of reusable sessions. The previous Home window showed a rudimentary grid of saved sessions, with no indication of what was running.

The new session list in action, showing a quick summary of each session as well as which are active or inactive.

For Audio Hijack 4, we wanted to make the session list an active part of the interface. It’s now possible to start or stop a session, view and adjust the Auto Run setting, quickly scan sources, check audio levels, and see status. The new Session List window is now a much more powerful starting point for using the app. It’s also easily expanded-upon, and in the future, we’re planning to add even more.

Animations Abound

Audio Hijack 4 is a kinetic app, with subtle animations to aid in understanding. The tiles and wires move, meters bounce, and status icons pulsate to show when things are in action. I’m proud of all these animations, but there are two particular bits I want to call out.

First up are the amazing animations on the connecting wires. While the previous version’s wires could occasionally look somewhat soft, Audio Hijack 4’s wires are all drawn with vectors, so they’re super sharp. They’re also beautifully curved and feel incredibly snappy as you drag blocks around.

You may not have noticed, but these wires actually morph shape. When a device isn’t running, the wire is made of arrows showing the direction audio will flow. When you hit ‘Run’, however, each arrow changes into a pill shape, as it starts moving and bouncing to represent the audio levels of the sound passing through that wire. Hit ‘Stop’ and every single blip on the wire morphs back into an arrow.

My other favorite animations are the various status badges which show what a given session is doing. Much like a photo on a cereal box, here they’ve been enlarged to show texture (I’ve also slowed them down):

In app, these animations are infinitely-looping, vector-based, and very cool.

Marketing Too

Animations also found their way into the app’s product marketing. Animated versions of the interface can be found on the main product marketing page for Audio Hijack, as well as the welcome window we show on first launch. Using still images just didn’t do justice to the dynamic app we’ve made. Getting these various videos working required a decent amount of troubleshooting, and a bit more file bandwidth. The extra work was well worth it, however, to show off the app in motion.

A New App Icon

One final thing I’d like to discuss is Audio Hijack’s new icon. App icons serve as the most recognizable symbol for a product, and Audio Hijack 4’s icon took a long time to nail down. It seems almost nothing is as prone to endless discussion and debate as icons.

Audio Hijack 3’s bottle icon was attractive and well drawn, but the “audio in a bottle” metaphor was a bit oblique. I did briefly try to modernize the bottle concept with my own take on it:

The original bottle icon on the left, with my sketch of a refresh on the right.

Ultimately, though, this never left the early sketch stages. I next tried using some abstract shapes as a base. I still love many of the designs I created. This page of my sketchbook is particularly pleasing:

Those sketches eventually led to more refined mockups, like this one:

I was very into both abstract patterns and this particular colour gradient, which does partly mirror the orange and blues of the app’s UI. However, while this waveform-inspired look was tangentially related to audio, it lacked a strong visual link to the rest of the app.

So it was that the slanted wavy pattern was tilted to vertical and changed to orange on a darker background, to match the meters inside the app. Finally, I added a physical microphone to more clearly communicate the concept of ‘audio’.

Many of us inside Rogue Amoeba lament the recent “flattening” of app icons on the Mac, and the attendant loss of personality. While I did feel we needed to somewhat conform to the new tile design paradigm, I wanted to overlay a bit of 3D to help differentiate the shape (see also: SoundSource).

Above is my first rendition of the concept with a 3D microphone. This icon is a lot more visually tied to the actual app it represents. Once I got here, we were close, though there was still plenty of tweaking and refining. Perhaps most interestingly, the final icon actually features two small Easter eggs: the waveform is based on a recording of me saying the word “Hijack”, and the mic reads RA 2002, representing the year Rogue Amoeba was founded1. Now you know!


I hope you enjoyed this peek at the design process for Audio Hijack 4. I was fortunate to work alongside a development team that was happy to spend time creating a wonderfully dynamic interface, one which shows off the useful new features and the rock-solid backend. I’m very pleased with how it all turned out.

However, I’ve only scratched the surface of all the new things you’ll see in Audio Hijack 4. I didn’t even mention major new features like manual pipeline connections or the new Global window. If you’ve used Audio Hijack before, be sure to give the “What’s New” page a look. Of course, if you’ve never used Audio Hijack, you ought to check out Audio Hijack 4 right here.


  1. Hey, that was 20 years ago! What a pleasingly round number. I doubt it will come up again anytime soon.↩︎

Our Software