Crossfader

Enabling everyone to remix anything

Ilias Karim
Jun 25, 2014 · 5 min read

Three and a half years ago, I downloaded a turntable app while walking on my way to class at Stanford. I had never DJed before in my life.

Just last month I performed on stage before thousands using Crossfader, a free iPhone app I developed with the company launched as “DJZ.com”

Today, 16 months after the launch of its first version, Crossfader 4 went live in the App Store. Like our community and the team itself the app is greater than the sum of its parts. But before features like Radio, Friends, and Packs became integral components of the product it was a very simple DJ app, perhaps even the simplest DJ app available on the market.

Audio Butcher

My part in shipping the initial, minimum, viable form of Crossfader with my colleagues actually began years earlier on three separate prototypes that would shape Crossfader named Audio Butcher, SoundCrate, and DJZ/U.

It was using an iPhone 4S — the first retina iPhone and my first Apple mobile device —that I still viscerally recall downloading my first turntable DJ app. I was on my way to Mobile Music, a software workshop instructed by Professor Ge Wang at Stanford’s Center for Computer Research in Music and Acoustics (CCRMA). That winter Electrical Engineering Ph.D. candidate Hyung-Suk Kim and I produced Audio Butcher for the class’s final project.

Audio Butcher, early 2011

As well-receieved as our prototype was around campus, we never released Audio Butcher despite the encouragement we received, especially from Ge. Nevertheless, we found our demo emphatically stated the case for a simpler mobile DJ app than anything that was currently out there.

SoundCrate

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Besides the mixing experience, there were more aspects of the creative process we wanted to explore as well, for instance music discovery.

Rather than build a social network ourselves, we imagined using SoundCloud as a platform for finding songs to remix and publishing those remixes. To test our assumptions we developed SoundCrate, a music discovery app.

SoundCrate v1, 2012

Coincidentally, musicians network in a way not unlike the way that academics do. Not only are musicians inspired by their own peers, whom they frequently collaborate with, but, they also publish their work in hopes among other goals of further inspiring others, just as do academics.

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SoundCrate v2, 2013

Coincidentally, musicians network in a way not unlike the way that academics do. Not only are musicians inspired by their own peers, whom they frequently collaborate with, but, they also publish their work in hopes among other goals of further inspiring others, just as do academics.

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DJZ/U

Over the course of developing SoundCrate, CCRMA classmate Gina Collechia introduced me to freshly-minted start-up DJZ.com. Backed by Union Square Ventures, Kleiner Perkins, Google Ventures, and many other investors, the DJZ.com team was planning a new app to educate the next generation of DJs.

DJZ is developing an iPhone app that teaches music fans how to DJ through a series of 10 interactive lessons. After completing lessons, the same app is used to perform live DJ sets. It teaches them the basics of DJing, supplies killer songs to start with, and then evolves with the user as their skills progress.

DJZ.com co-founder Andy Chimicles to Seth Goldstein in December, 2012

The initial designs for DJZ/U (U as in university) intended the product to be a sort of tutorial or DJ-training-wheels with an interface that added new elements with each stage the user completed until the user graduated to a complete set of DJ tools at their fingertips.

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Prototype, January 2013

We observed, however, that nearly every interface element added after the first stage of the tutorial detracted from the overall DJing experience. The iPhone display was either too small or there were too many elements on the screen, making them too hard to manipulate with skill, dexterity and ease.

Backstage at Ruby Skye one night in San Francisco we got to talking while advisor Paul Oakenfold performed beside us. Seth raised the question, “what if we used the device’s sensors to control the music?”

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Our conversation reminded me of what I’d learned from Ge at CCRMA. In 2008, Ge created the App Store’s first hit music app the Ocarina, which turned the device into a flute-like instrument and thereby its users into performers.

Likewise, by using the iPhone’s gyroscope and accelerometer to crossfade and to control effects we created Crossfader, a first of its kind musical instrument.

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Prototype, February, 2013

Reducing the number of UI elements 1-by-1 as we leveraged the apps senors more compelled us to innovate in other ways, too.

We needed a way to load songs so they always played in sync. Co-founder Jake Lamante devised a plan to phrase-match and key-match songs, making it certain that anyone would always sound awesome with the app.

In April 2013 Crossfader made its App Store debut featuring just 42 30-second loops and 3 5-second long samples.

Remix Everything

The story behind the app Crossfader

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