We haven't gotten to the bottom of this yet, but we thought you might like to know: apparently, the Ion Audio Guitar Apprentice we showed you at CES last week is embroiled in a patent infringement debate right now. FutureMusic reports that Behringer (yes, the one with the 10,000 watt iPod dock) served Ion Audio with a cease-and-desist letter right on the show floor, claiming the Guitar Apprentice infringes a patent it filed over a year ago. Sure enough, Behringer does indeed have a patent for a "touch screen guitar" — which was coincidentally granted on the very day of CES — and though we couldn't find a working prototype of the Behringer iAxe at the show, we suspect it might exist.

Oh, but there's more: the name "Guitar Apprentice" is also trademarked by a company called Legacy Learning Systems for "interactive multimedia programs," namely, the Guitar Apprentice series of instructional videos on how to play guitar. That might be a different enough product that one could argue consumer confusion isn't likely, but still: FutureMusic contacted the company's CEO, who apparently wasn't too pleased and suggested that he might pursue legal action too.

We won't comment on the strength of Behringer's patent, and the company wouldn't comment on the whole proceedings when we asked at NAMM today, but it sounds like the world might not be big enough for a pair of iPad-wielding axes. We'll let you know if Ion Audio (aka Numark) gets a court date.