Hi,
Thanks for your reply. FYI I have found a workable solution for the Mac (but not for Windows)
Install the free audio recorder iScream from https://www.mediahuman/iscream/ – it simply records the output of your sound card until you stop it by clicking the icon which lives on the task bar.
What is useful is that you can download the mp3 (not WAV) into Audition and edit as normal whilst the iScream recording continues.
Drawbacks: Audition doesn’t support live file update – as it sees the same file name it doesn’t load the newer version, you have to close the file but when you reload you get the entire file up to the point of clicking Open. Also don’t click ‘Save’ – this crashes Audition, use ‘Save As’ or ‘Save Selection’ and rename the file.
Upside: The iScream program just carries on recording!