You shouldn't need to be in record mode but you do need to be able monitor the input.

Trying to remember how you do in 10.6.x using the audio input but give this a try: In Audio MIDI Setup.app, make sure that your Audio In is present and set to the same sample rate as BIAB. Now, when in BIAB, check System Preferences/Sound and make sure that your Audio Input (and not your microphone, Soundflower etc.) is selected as your In. Make sure that BIAB is using the same In.


Newer Macs since ??? no longer have an Audio Input including my 2017 iMac Pro and my wife's 2020 iMac (headphone outs only)—non't think my wife's and daughters' 2015 laptops do (my 2012 MBP does, however). This is easy with any compatible audio interface. Unfortunately, none of the inexpensive new ones will work for you—they support Core Audio but not before OS 10.11.x El Capitán. You need an older one that supports Core Audio in OS 10.6 or one that has compatible drivers. You then enable the track to monitor the audio without arming the Record button same as above.

BTW, I only check this board when someone messages me that there's a question I might be able to answer. I would have seen it days ago in the Macintosh board. This hasn't been a frequently asked question for over a decade.

BIAB 2024 Audiophile Mac
24Core/60CoreGPU M2 MacStudioUltra/8TB/192GB Sequoia, M1 MBAir, 2012 MBP
Digital Performer11, LogicPro, Finale27/Dorico/Encore/SmartScorePro64/Notion6 /Overture5