Waveforms not displaying on most tracks
On some projects, the waveforms are displaying as flat or nearly flat lines on most tracks. As it happens, the tracks I can't edit are the ones I need to edit. They are all real instrument tracks recorded through a USB - guitar interface. When I go to flex time I see flex lines but no waves. Does anyone have any idea what to do about this?
Thanks
MacBook Air, OS X Yosemite (10.10.2)