I'm trying to re-implement the PlaySoftMIDI example from the Xcode installation in MacRuby, but am getting parameter errors. Could some kind soul point me in the right direction? Below is a small example that ends with a parameter error. The call to NewAUGraph appears to work, returning a zero, but the call to AUGraphAddNode returns -50. framework 'AudioToolbox' framework 'AudioUnit' load_bridge_support_file 'bridgesupport/Application.bridgesupport' load_bridge_support_file 'bridgesupport/AudioToolbox.bridgesupport' load_bridge_support_file 'bridgesupport/AudioUnit.bridgesupport' outGraph = Pointer.new_with_type '^{OpaqueAUGraph}' result = NewAUGraph outGraph # returns 0 puts result cd = ComponentDescription.new cd.componentManufacturer = KAudioUnitManufacturer_Apple cd.componentType = KAudioUnitType_MusicDevice cd.componentSubType = KAudioUnitSubType_DLSSynth cd_ptr = Pointer.new_with_type '{ComponentDescription=IIIII}' cd_ptr.assign cd synthNode = Pointer.new_with_type 'i' result = AUGraphAddNode outGraph[0], cd_ptr, synthNode # returns -50 puts result I generated the bridge support files with gen_bridge_metadata -f AudioToolbox -o AudioToolbox.bridgesupport gen_bridge_metadata -f AudioUnit -o AudioUnit.bridgesupport The Application.bridgesupport file contains struct and cftype definitions for ComponentDescription. They were generated using a header file since I couldn't figure out how to generate them from the CarbonCore framework directly. Any help would be appreciated. Thanks, Ed