Algoriddim's popular mixing app djay is a lesson in mass appeal. If you see yourself playing in clubs and festivals, you'll likely be reaching for software like Serato, or Traktor. But, if you have a phone or a tablet (and a penchant for the old turntable setup, albeit virtual) then djay is an easy choice. So much so that 15 million of you have downloaded it to date. The app broke out of its mobile scheckles some time ago, with a Mac OS X version, for those that wanted to look a little more serious. Today, Algoriddim is hoping to pick up a few more dedicated DJs with the launch of djay Pro, an even more advanced version (also for Mac).