sound studios

Use GarageBand to record your cassette audio. Configure recording to a stereo audio track via the cassette player input to a USB port. You can record the entire tape, then export regions (songs) to individual files for import into the Music app or other use.

Use the Audio MIDI Setup app (find in Applications > Utilities folder) to configure the USB input for the cassette (I think).

Before you worry about which app you need, you best check whatever ports your iMac has and what cassette player you have and how to connect it to your Mac. You need to check your Mac's ports to make sure you have one that allows sound in and then find a cable that'll fit that as well as your cassette player. You can then import the songs and get an app that'll work. I am running an older OS and Sound Studio was always great to use; check on it to see if it'll be compatible with Big Sur.

You’re welcome. Am happy to know you were able to work it out, my friend.