I'm trying to write develop audio related application. In that, I'm using AudioToolBox framework for recording the sound. And I'm using AVFramework to play soudns. When app is stared, it will play some mp3 file using AVFramework. And also initializes Audiotoolbox. In simulator, I'm able to record and play. But when I'm testing it on iPhone, I'm getting following error for initializing AudioToolBox. 2009-12-11 22:25:51.599 StoryBook[807:207] AudioRecorder init AudioSessionInitialize failed with error: 1768843636 Can some one tell me whether we can use both AV as well as Audio Toolbox frame works in one application? Why I'm getting that error? --Satyam.