Early 2009 MacPro. This minor issue has nothing to do with audio within or from BIAB, it is only the nuisance of having to re-assign MIDI output ports each time the app is launched. Once this is done, everything is normal. The external synths are not, judging from inactive activity lights, receiving MIDI data from BIAB without user intervention, so it doesn't really matter how the audio output from the synths is dealt with, there is no audio output because there is no MIDI input. It clearly seems to be that the 'remembered' port assignments are not active until the port selection dialog is brought up and the 'ok' selected. Then MIDI data again reaches the synths and everything is quite normal.