Algoriddim's Djay is a $49.95 Mac application that lets you spin your iTunes library in a virtual two-turntable setup.
Djay's interface stays fairly faithful to the old-school turntablist tradition, with a crossfader, cue points (which let you mark a record at specific spots so you can move the stylus to the desired part of a song), and virtual "scratching," enabled by dragging your cursor across the vinyl on the screen. At the same time, Djay offers digital conveniences such as automatic beat matching and tempo synchronization. In addition, its Automix feature creates a mix on the fly from your playlists.
Djay isn't new--version 3.1 was released in February. But in March, Algoriddim launched an iPhone app that lets you control Djay remotely from your iPhone or iPod Touch. I tested the first update to Djay Remote, which was released last week and offers better network performance than the original version, and it's a pretty straightforward experience, if you're familiar with the desktop app.
To use Djay Remote, you have to make sure your iPhone or iPod Touch is connected to the same Wi-Fi network as your Mac, then accept the prompt on the Mac app to let Djay Remote take over. Once you're connected, the iPhone app lets you pick songs from the Mac's iTunes library (not the iTunes library on the phone, which is off-limits to apps), and gives you control over both turntables. You can also match tempos, create simple loops, and add various effects.
The performance of the app was outstanding over my 802.11g network. I entered commands on the phone, and the Mac responded immediately, even when I was on a completely different level of my house. My only complaint about the iPhone app is the price--$4.99 is a bit expensive for a fairly simple remote-control app, especially if you've already plunked down fifty bucks for the full Mac application.