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Wednesday, May 11, 2011

Smartphone turntables put new spin on DJing



Scratching - moving a vinyl record back and forth while it's playing to produce a distinctive sound - is a mainstay of the DJing profession, but one that's threatened by the change from records to a laptop full of MP3s. Now, DJs can now transform their analogue turntables into the digital variety by placing a smartphone on top of their record, providing a whole new way to scratch.

Nicholas Bryan, who researches music, computing and design at Stanford University, has developed an app that uses an iPod Touch or iPhone's accelerometer and gyroscope to detect a DJ's scratching motion. These sensors aren't very precise, but because scratching is limited to a circular motion it is easy to extract the centripetal force and thus the rotational velocity of the scratch. The data is then wirelessly transmitted to the DJ's computer to manipulate its audio playback.

Digital turntables that let DJs scratch CDs or MP3s already exist, but Bryan says his system, called MOPHO DJ, offers a number of advantages. It lets DJs use their old equipment with little-to-no modification - Bryan made a plexiglass disc to hold his iPhone in place, but say you could easily just use an old record instead. "This allows one turntable to easily be used for both analog and digital scratching and provides a similar feel to the musician," he says.

The system can also take advantage of the iPhone's screen to display a real-time audio waveform or apply additional audio effects. DJs can even forgo turntables entirely, and pick up their phone for a spot of "air scratching". Bryan will present the system at the New Interfaces for Musical Expression conference in Norway at the end of May, and plans to release the iPhone app and accompanying DJ software in the future.
newscientist 

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